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Almohanna AM, Noble K, Wray S. Extracellular acidification increases uterine contraction in pregnant mouse by increasing intracellular calcium. Acta Physiol (Oxf) 2024; 240:e14147. [PMID: 38650469 DOI: 10.1111/apha.14147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 03/07/2024] [Accepted: 04/05/2024] [Indexed: 04/25/2024]
Abstract
AIMS As uterine extracellular pH decreases during the ischemic conditions of labor, but its effects on myometrial contraction are largely unknown, there is a need to elucidate its physiological effects and mechanisms of action. Furthermore, it is not known if any of the effects of extracellular acidification are affected by pregnancy, thus we also determined how gestation affects the response to acidification. METHODS Nonpregnant, mid-, and term-pregnant myometrial strips were obtained from humanely killed mice. Contractions were recorded under spontaneous, depolarized, and oxytocin-stimulated conditions. The extracellular pH of the perfusate was changed from 7.4 to 6.9 or 7.9 in HEPES-buffered physiological saline. Intracellular pH was measured using SNARF, and intracellular calcium was measured using Indo-1. Statistical differences were tested using the appropriate t-test. RESULTS Extracellular acidification significantly increased the frequency and amplitude of spontaneous contractions in pregnant, but not nonpregnant, myometrium, whereas alkalinization decreased contractions. Intracellular acidification, via Na-butyrate, transiently increased force in pregnant tissue. Intracellular pH was gradually acidified when extracellular pH was acidified, but extracellular acidification increased contractility before any significant change in intracellular pH. If myometrial force was driven by oxytocin or high-K depolarization, then extracellular pH did not further increase force. Intracellular calcium changes mirrored those of force in the spontaneously contracting pregnant myometrium, and if calcium entry was prevented by nifedipine, extracellular acidification could not induce a rise in force. CONCLUSION Extracellular acidification increases excitability, calcium entry, and thus force in pregnant mouse myometrium, and this may contribute to increasing contractions during labor when ischemic conditions and acidemia occur.
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Affiliation(s)
- Asmaa M Almohanna
- Department of Basic Science, College of Medicine, Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Karen Noble
- Department of Veterinary Anatomy, Physiology and Pathology Institute of Infection, Veterinary and Ecological Sciences University of Liverpool, Liverpool, UK
| | - Susan Wray
- Department of Women and Children's Health, Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
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2
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Carr JMJR, Caldwell HG, Ainslie PN. Cerebral blood flow, cerebrovascular reactivity and their influence on ventilatory sensitivity. Exp Physiol 2021; 106:1425-1448. [PMID: 33932955 DOI: 10.1113/ep089446] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2021] [Accepted: 04/26/2021] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the topic of this review? Cerebrovascular reactivity to CO2 , which is a principal factor in determining ventilatory responses to CO2 through the role reactivity plays in determining cerebral extra- and intracellular pH. What advances does it highlight? Recent animal evidence suggests central chemoreceptor vasculature may demonstrate regionally heterogeneous cerebrovascular reactivity to CO2 , potentially as a protective mechanism against excessive CO2 washout from the central chemoreceptors, thereby allowing ventilation to reflect the systemic acid-base balance needs (respiratory changes in P aC O 2 ) rather than solely the cerebral needs. Ventilation per se does not influence cerebrovascular reactivity independent of changes in P aC O 2 . ABSTRACT Alveolar ventilation and cerebral blood flow are both predominantly regulated by arterial blood gases, especially arterial P C O 2 , and so are intricately entwined. In this review, the fundamental mechanisms underlying cerebrovascular reactivity and central chemoreceptor control of breathing are covered. We discuss the interaction of cerebral blood flow and its reactivity with the control of ventilation and ventilatory responsiveness to changes in P C O 2 , as well as the lack of influence of ventilation itself on cerebrovascular reactivity. We briefly summarize the effects of arterial hypoxaemia on the relationship between ventilatory and cerebrovascular response to both P C O 2 and P O 2 . We then highlight key methodological considerations regarding the interaction of reactivity and ventilatory sensitivity, including the following: regional heterogeneity of cerebrovascular reactivity; a pharmacological approach for the reduction of cerebral blood flow; reactivity assessment techniques; the influence of mean arterial blood pressure; and sex-related differences. Finally, we discuss ventilatory and cerebrovascular control in the context of high altitude and congestive heart failure. Future research directions and pertinent questions of interest are highlighted throughout.
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Affiliation(s)
- Jay M J R Carr
- Centre for Heart, Lung and Vascular Health, University of British Columbia - Okanagan Campus, British Columbia, Canada
| | - Hannah G Caldwell
- Centre for Heart, Lung and Vascular Health, University of British Columbia - Okanagan Campus, British Columbia, Canada
| | - Philip N Ainslie
- Centre for Heart, Lung and Vascular Health, University of British Columbia - Okanagan Campus, British Columbia, Canada
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3
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Duffin J, Mikulis DJ, Fisher JA. Control of Cerebral Blood Flow by Blood Gases. Front Physiol 2021; 12:640075. [PMID: 33679453 PMCID: PMC7930328 DOI: 10.3389/fphys.2021.640075] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 01/25/2021] [Indexed: 12/19/2022] Open
Abstract
Cerebrovascular reactivity can be measured as the cerebrovascular flow response to a hypercapnic challenge. The many faceted responses of cerebral blood flow to combinations of blood gas challenges are mediated by its vasculature's smooth muscle and can be comprehensively described by a simple mathematical model. The model accounts for the blood flow during hypoxia, anemia, hypocapnia, and hypercapnia. The main hypothetical basis of the model is that these various challenges, singly or in combination, act via a common regulatory pathway: the regulation of intracellular hydrogen ion concentration. This regulation is achieved by membrane transport of strongly dissociated ions to control their intracellular concentrations. The model assumes that smooth muscle vasoconstriction and vasodilation and hence cerebral blood flow, are proportional to the intracellular hydrogen ion concentration. Model predictions of the cerebral blood flow responses to hypoxia, anemia, hypocapnia, and hypercapnia match the form of observed responses, providing some confidence that the theories on which the model is based have some merit.
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Affiliation(s)
- James Duffin
- Department of Anesthesia and Pain Management, University of Toronto, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Thornhill Research Inc., Toronto, ON, Canada
- University Health Network, Toronto, ON, Canada
| | - David J. Mikulis
- Division of Neuroradiology Imaging, Joint Department of Medical Imaging, University Health Network, Toronto, ON, Canada
| | - Joseph A. Fisher
- Department of Anesthesia and Pain Management, University of Toronto, Toronto, ON, Canada
- Department of Physiology, University of Toronto, Toronto, ON, Canada
- Thornhill Research Inc., Toronto, ON, Canada
- University Health Network, Toronto, ON, Canada
- Faculty of Medicine, Institute of Medical Science, University of Toronto, Toronto, ON, Canada
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Guanosine, a guanine-based nucleoside relaxed isolated corpus cavernosum from mice through cGMP accumulation. Purinergic Signal 2020; 16:241-249. [PMID: 32458299 DOI: 10.1007/s11302-020-09702-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Accepted: 05/01/2020] [Indexed: 10/24/2022] Open
Abstract
In corpus cavernosum (CC), guanosine triphosphate (GTP) is converted into cyclic guanosine monophosphate (cGMP) to induce erection. The action of cGMP is terminated by phosphodiesterases and efflux transporters, which pump cGMP out of the cell. The nucleotides, GTP, and cGMP were detected in the extracellular space, and their hydrolysis lead to the formation of intermediate products, among them guanosine. Therefore, our study aims to pharmacologically characterize the effect of guanosine in isolated CC from mice. The penis was isolated and functional and biochemical analyses were carried out. The guanine-based nucleotides GTP, guanosine diphosphate, guanosine monophosphate, and cGMP relaxed mice corpus cavernosum, but the relaxation (90.7 ± 12.5%) induced by guanosine (0.000001-1 mM) was greater than that of the nucleotides (~ 45%, P < 0.05). Guanosine-induced relaxation was not altered in the presence of adenosine type 2A and 2B receptor antagonists. No augment was observed in the intracellular levels of cyclic adenosine monophosphate in tissues stimulated with guanosine. Inhibitors of nitric oxide synthase (L-NAME, 100 μM) and soluble guanylate cyclase (ODQ, 10 μM) produced a significant reduction in guanosine-induced relaxation in all concentrations studied, while in the presence of tadalafil (300 nM), a significant increase was observed. Pre-incubation of guanosine (100 μM) produced a 6.6-leftward shift in tadalafil-induced relaxation. The intracellular levels of cGMP were greater when CC was stimulated with guanosine. Inhibitors of ecto-nucleotidases and xanthine oxidase did not interfere in the response induced by guanosine. In conclusion, our study shows that guanosine relaxes mice CC and opens the possibility to test its role in models of erectile dysfunction.
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Jiang S, Wang X, Wei J, Zhang G, Zhang J, Xie P, Xu L, Wang L, Zhao L, Li L, Wilcox CS, Chen J, Lai EY, Liu R. NaHCO 3 Dilates Mouse Afferent Arteriole Via Na +/HCO 3- Cotransporters NBCs. Hypertension 2019; 74:1104-1112. [PMID: 31522618 DOI: 10.1161/hypertensionaha.119.13235] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Sodium bicarbonate has long been used to treat chronic kidney disease. It has been demonstrated to slow the decline in glomerular filtration rate in chronic kidney disease patient; however, the mechanisms are not completely understood. We hypothesized that NaHCO3 dilates afferent arterioles (Af-Art) by stimulating nitric oxide (NO) release mediated by the Na+/HCO3- cotransporter (NBC) contributing to the elevation in glomerular filtration rate. Isolated microperfused mouse renal Af-Art, preconstricted with norepinephrine (1 µmol/L), dilated 45±2% (n=6, P<0.05) in response to NaHCO3 (44 mmol/L). Whereas, NaCl solution containing the same Na+ concentration was not effective. The mRNA for NBCn1 and NBCe1 were detected in microdissected Af-Art using reverse transcription-polymerase chain reaction and quantitative polymerase chain reaction. The Af-Art intracellular pH measured with 2',7'-bis-(2-carboxyethyl)-5-(and-6) carboxyfluorescein, acetoxymethyl ester increased significantly by 0.29±0.02 (n=6; P<0.05) in the presence of NaHCO3, which was blunted by N-cyanosulphonamide compound (S0859) that is an inhibitor of the NBC family. After clamping the intracellular pH with 10 μM nigericin, changing the bath solution pH from 7.4 to 7.8 still dilates the Af-Art by 53±4% (n=7; P<0.005) and increases NO generation by 22±3% (n=7; P<0.005). Both pH-induced NO generation and vasodilation were blocked by L-NG-Nitroarginine Methyl Ester. NaHCO3 increased NO generation in Af-Art by 19±4% (n=5; P<0.005) and elevated glomerular filtration rate in conscious mice by 36% (233 versus 318 ul/min; n=9-10; P<0.0001). S0859 and L-NG-nitroarginine methyl ester blocked NaHCO3-induced increases in NO generation and vasodilation. We conclude that NBCn1 and NBCe1 are expressed in Af-Art and that NaHCO3 dilates Af-Art via NBCs mediated by NO that increases the glomerular filtration rate.
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Affiliation(s)
- Shan Jiang
- From Kidney Disease Center, the First Affiliated Hospital, and Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China (S.J., G.Z., P.X., L.Z., L.L., J.C., E.Y.L.).,Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (S.J., X.W., J.W., G.Z., J.Z., L.W., R.L.)
| | - Ximing Wang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (S.J., X.W., J.W., G.Z., J.Z., L.W., R.L.).,Shandong Provincial Hospital, Affiliated Hospital of Shandong University, Jinan, China (X.W.)
| | - Jin Wei
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (S.J., X.W., J.W., G.Z., J.Z., L.W., R.L.)
| | - Gensheng Zhang
- From Kidney Disease Center, the First Affiliated Hospital, and Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China (S.J., G.Z., P.X., L.Z., L.L., J.C., E.Y.L.).,Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (S.J., X.W., J.W., G.Z., J.Z., L.W., R.L.)
| | - Jie Zhang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (S.J., X.W., J.W., G.Z., J.Z., L.W., R.L.)
| | - Peng Xie
- From Kidney Disease Center, the First Affiliated Hospital, and Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China (S.J., G.Z., P.X., L.Z., L.L., J.C., E.Y.L.)
| | - Lan Xu
- College of Public Health, University of South Florida, Tampa (L.X.)
| | - Lei Wang
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (S.J., X.W., J.W., G.Z., J.Z., L.W., R.L.)
| | - Liang Zhao
- From Kidney Disease Center, the First Affiliated Hospital, and Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China (S.J., G.Z., P.X., L.Z., L.L., J.C., E.Y.L.).,Department of Physiology, School of Basic Medical Sciences, Guangzhou Medical University, China (L.Z., E.Y.L.).,Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Humboldt-Universität zu Berlin, Germany (L.Z., E.Y.L.)
| | - Lingli Li
- From Kidney Disease Center, the First Affiliated Hospital, and Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China (S.J., G.Z., P.X., L.Z., L.L., J.C., E.Y.L.).,Division of Nephrology and Hypertension, and Hypertension Center, Georgetown University, Washington, DC (L.L., C.S.W.)
| | - Christopher S Wilcox
- Division of Nephrology and Hypertension, and Hypertension Center, Georgetown University, Washington, DC (L.L., C.S.W.)
| | - Jianghua Chen
- From Kidney Disease Center, the First Affiliated Hospital, and Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China (S.J., G.Z., P.X., L.Z., L.L., J.C., E.Y.L.)
| | - En Yin Lai
- From Kidney Disease Center, the First Affiliated Hospital, and Department of Physiology, School of Basic Medical Sciences, Zhejiang University School of Medicine, Hangzhou, China (S.J., G.Z., P.X., L.Z., L.L., J.C., E.Y.L.).,Department of Physiology, School of Basic Medical Sciences, Guangzhou Medical University, China (L.Z., E.Y.L.).,Institute of Vegetative Physiology, Charité-Universitätsmedizin Berlin, Humboldt-Universität zu Berlin, Germany (L.Z., E.Y.L.)
| | - Ruisheng Liu
- Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa (S.J., X.W., J.W., G.Z., J.Z., L.W., R.L.)
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Charter ME, Lamb IR, Murrant CL. Arteriolar and capillary responses to CO2and H+in hamster skeletal muscle microvasculature: Implications for active hyperemia. Microcirculation 2018; 25:e12494. [DOI: 10.1111/micc.12494] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 06/21/2018] [Accepted: 07/18/2018] [Indexed: 12/20/2022]
Affiliation(s)
- Mackenzie E. Charter
- Department of Human Health and Nutritional Sciences; University of Guelph; Guelph Ontario Canada
| | - Iain R. Lamb
- Department of Human Health and Nutritional Sciences; University of Guelph; Guelph Ontario Canada
| | - Coral L. Murrant
- Department of Human Health and Nutritional Sciences; University of Guelph; Guelph Ontario Canada
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7
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Aleksandrowicz M, Dworakowska B, Dolowy K, Kozniewska E. Restoration of the response of the middle cerebral artery of the rat to acidosis in hyposmotic hyponatremia by the opener of large-conductance calcium sensitive potassium channels (BK Ca). J Cereb Blood Flow Metab 2017; 37:3219-3230. [PMID: 28058990 PMCID: PMC5584697 DOI: 10.1177/0271678x16685575] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Hyposmotic hyponatremia (the decrease of extracellular concentration of sodium ions from 145 to 121 mM and the decrease of hyposmolality from 300 to 250 mOsm/kg H2O) impairs response of the middle cerebral artery (MCA) to acetylcholine and NO donor (S-nitroso-N-acetyl-DL-penicillamine). Since acidosis activates a similar intracellular signaling pathway, the present study was designed to verify the hypothesis that the response of the MCA to acidosis is impaired during acute hyposmotic hyponatremia due to abnormal NO-related signal transduction in vascular smooth muscle cells. Studies performed on isolated, cannulated, and pressurized rat MCA revealed that hyposmotic hyponatremia impaired the response of the MCA to acidosis and this was associated with hyposmolality rather than with decreased sodium ion concentration. Response to acidosis was restored by the BKCa but not by the KATP channel activator. Patch-clamp electrophysiology performed on myocytes freshly isolated from MCAs, demonstrated that hyposmotic hyponatremia does not affect BKCa currents but decreases the voltage-dependency of the activation of the BKCa channels in the presence of a specific opener of these channels. Our study suggests that reduced sensitivity of BKCa channels in the MCA to agonists results in the lack of response of this artery to acidosis during acute hyposmotic hyponatremia.
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Affiliation(s)
- Marta Aleksandrowicz
- 1 Department of Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland
| | - Beata Dworakowska
- 2 Department of Biophysics, Warsaw University of Life Sciences, Warsaw, Poland
| | - Krzysztof Dolowy
- 2 Department of Biophysics, Warsaw University of Life Sciences, Warsaw, Poland
| | - Ewa Kozniewska
- 1 Department of Neurosurgery, Mossakowski Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.,3 Department of Experimental and Clinical Physiology, Medical University of Warsaw, Warsaw, Poland
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Ng FL, Boedtkjer E, Witkowska K, Ren M, Zhang R, Tucker A, Aalkjær C, Caulfield MJ, Ye S. Increased NBCn1 expression, Na+/HCO3- co-transport and intracellular pH in human vascular smooth muscle cells with a risk allele for hypertension. Hum Mol Genet 2017; 26:989-1002. [PMID: 28087731 PMCID: PMC5409084 DOI: 10.1093/hmg/ddx015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 12/21/2016] [Accepted: 12/30/2016] [Indexed: 02/05/2023] Open
Abstract
Genome-wide association studies have revealed an association between variation at the SLC4A7 locus and blood pressure. SLC4A7 encodes the electroneutral Na+/HCO3- co-transporter NBCn1 which regulates intracellular pH (pHi). We conducted a functional study of variants at this locus in primary cultures of vascular smooth muscle and endothelial cells. In both cell types, we found genotype-dependent differences for rs13082711 in DNA-nuclear protein interactions, where the risk allele is associated with increased SLC4A7 expression level, NBCn1 availability and function as reflected in elevated steady-state pHi and accelerated recovery from intracellular acidosis. However, in the presence of Na+/H+ exchange activity, the SLC4A7 genotypic effect on net base uptake and steady-state pHi persisted only in vascular smooth muscle cells but not endothelial cells. We found no discernable effect of the missense polymorphism resulting in the amino acid substitution Glu326Lys. The finding of a genotypic influence on SLC4A7 expression and pHi regulation in vascular smooth muscle cells provides an insight into the molecular mechanism underlying the association of variation at the SLC4A7 locus with blood pressure.
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Affiliation(s)
- Fu Liang Ng
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Kate Witkowska
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Meixia Ren
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Ruoxin Zhang
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Arthur Tucker
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Christian Aalkjær
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Biomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Mark J. Caulfield
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
- To whom correspondence should be addressed at: Heart Centre, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, UK. Tel: +44 2078823403; Fax: +44 2078823408; (M.J.C.); Department of Cardiovascular Sciences, University of Leicester, BHF Cardiovascular Research Centre, Glenfield Hospital, Leicester LE3 9QP, UK. Tel: +44 1162044754; Fax: +44 1162875792; (S.Y.)
| | - Shu Ye
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
- NIHR Biomedical Research Centre in Cardiovascular Disease, Leicester, UK
- Shantou University Medical College, Shantou, China
- To whom correspondence should be addressed at: Heart Centre, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, UK. Tel: +44 2078823403; Fax: +44 2078823408; (M.J.C.); Department of Cardiovascular Sciences, University of Leicester, BHF Cardiovascular Research Centre, Glenfield Hospital, Leicester LE3 9QP, UK. Tel: +44 1162044754; Fax: +44 1162875792; (S.Y.)
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Fennell VS, Kalani MYS, Atwal G, Martirosyan NL, Spetzler RF. Biology of Saccular Cerebral Aneurysms: A Review of Current Understanding and Future Directions. Front Surg 2016; 3:43. [PMID: 27504449 PMCID: PMC4958945 DOI: 10.3389/fsurg.2016.00043] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Accepted: 07/06/2016] [Indexed: 12/24/2022] Open
Abstract
Understanding the biology of intracranial aneurysms is a clinical quandary. How these aneurysms form, progress, and rupture is poorly understood. Evidence indicates that well-established risk factors play a critical role, along with immunologic factors, in their development and clinical outcomes. Much of the expanding knowledge of the inception, progression, and rupture of intracranial aneurysms implicates inflammation as a critical mediator of aneurysm pathogenesis. Thus, therapeutic targets exploiting this arm of aneurysm pathogenesis have been implemented, often with promising outcomes.
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Affiliation(s)
- Vernard S Fennell
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center , Phoenix, AZ , USA
| | - M Yashar S Kalani
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center , Phoenix, AZ , USA
| | - Gursant Atwal
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center , Phoenix, AZ , USA
| | - Nikolay L Martirosyan
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center , Phoenix, AZ , USA
| | - Robert F Spetzler
- Department of Neurosurgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center , Phoenix, AZ , USA
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Boedtkjer E, Hansen KB, Boedtkjer DMB, Aalkjaer C, Boron WF. Extracellular HCO3- is sensed by mouse cerebral arteries: Regulation of tone by receptor protein tyrosine phosphatase γ. J Cereb Blood Flow Metab 2016; 36:965-80. [PMID: 26661205 PMCID: PMC4853837 DOI: 10.1177/0271678x15610787] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/15/2015] [Indexed: 11/15/2022]
Abstract
We investigate sensing and signaling mechanisms for H(+), [Formula: see text] and CO2 in basilar arteries using out-of-equilibrium solutions. Selectively varying pHo, [[Formula: see text]]o, or pCO2, we find: (a) lowering pHo attenuates vasoconstriction and vascular smooth muscle cell (VSMC) Ca(2+)-responses whereas raising pHo augments vasoconstriction independently of VSMC [Ca(2+)]i, (b) lowering [[Formula: see text]]o increases arterial agonist-sensitivity of tone development without affecting VSMC [Ca(2+)]i but c) no evidence that CO2 has direct net vasomotor effects. Receptor protein tyrosine phosphatase (RPTP)γ is transcribed in endothelial cells, and direct vasomotor effects of [Formula: see text] are absent in arteries from RPTPγ-knockout mice. At pHo 7.4, selective changes in [[Formula: see text]]o or pCO2 have little effect on pHi At pHo 7.1, decreased [[Formula: see text]]o or increased pCO2 causes intracellular acidification, which attenuates vasoconstriction. Under equilibrated conditions, anti-contractile effects of CO2/[Formula: see text] are endothelium-dependent and absent in arteries from RPTPγ-knockout mice. With CO2/[Formula: see text] present, contractile responses to agonist-stimulation are potentiated in arteries from RPTPγ-knockout compared to wild-type mice, and this difference is larger for respiratory than metabolic acidosis. In conclusion, decreased pHo and pHi inhibit vasoconstriction, whereas decreased [[Formula: see text]]o promotes vasoconstriction through RPTPγ-dependent changes in VSMC Ca(2+)-sensitivity. [Formula: see text] serves dual roles, providing substrate for pHi-regulating membrane transporters and modulating arterial responses to acid-base disturbances.
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Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | | | - Donna M B Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | | | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
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Hanley JA, Weeks A, Wray S. Physiological increases in lactate inhibit intracellular calcium transients, acidify myocytes and decrease force in term pregnant rat myometrium. J Physiol 2015. [PMID: 26223765 PMCID: PMC4606541 DOI: 10.1113/jp270631] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Key points Lactate is increased in myometrial capillary blood from women in slow or non‐progressive labour (dystocia), suggesting that it is detrimental to uterine contractions. There are no studies of the effect of lactate on the myometrium. In the present study, we have investigated its effects and mechanism of action on myometrial strips from term pregnant rats. We show that lactate significantly decreased spontaneous contractility. Lactatedecreased pHi and inhibited Ca2+ transients. Nulling the decrease in pHi abolished the effects of lactate effects. If Ca2+ entry was enhanced, the effects of lactate were abolished. The present study suggests that the accumulation of extracellular lactate could contribute to labour dystocia.
Abstract Lactate is increased in myometrial capillary blood from women in slow or non‐progressive labour (dystocia), suggesting that it is detrimental to uterine contractions. There are, however, no studies of the effect of lactate on the myometrium. We therefore investigated its effects and mechanism of action on myometrial strips from term pregnant rats. The effects on spontaneous and oxytocin‐induced contractility in response to sodium lactate and other weak acids (1–20 mM) were studied. In some experiments, simultaneous force and intracellular Ca2+ or pH (pHi) were measured with Indo‐1 or Carboxy‐SNARF, respectively. Statistical differences were tested using non‐parametric tests. Lactate significantly decreased spontaneous contractility with an EC50 of 3.9 mM. Propionate, butyrate and pyruvate also reduced contractions with similar potency. The effects of lactate were reduced in the presence of oxytocin but remained significant. Lactate decreased pHi and nulling the decrease in pHi abolished its effects. We also show that lactate inhibited Ca2+ transients, with these changes mirroring those produced on force. If Ca2+ entry was enhanced by depolarization (high KCl) or applying the Ca2+ channel agonist, Bay K 4644, the effects of lactate were abolished. Taken together, these data show that lactate in the physiological range potently decreases myometrial contractility as a result of its inhibition of Ca2+ transients, which can be attributed to the induced acidification. The present study suggests that the accumulation of extracellular lactate will reduce myometrial contractions and could therefore contribute to labour dystocia.
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Affiliation(s)
| | - Andrew Weeks
- Women's and Children's Health, Institute of Translational Medicine, University of Liverpool, Liverpool, UK
| | - Susan Wray
- Departments of Cellular and Molecular Physiology
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Kimmoun A, Novy E, Auchet T, Ducrocq N, Levy B. Hemodynamic consequences of severe lactic acidosis in shock states: from bench to bedside. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2015; 19:175. [PMID: 25887061 PMCID: PMC4391479 DOI: 10.1186/s13054-015-0896-7] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Lactic acidosis is a very common biological issue for shock patients. Experimental data clearly demonstrate that metabolic acidosis, including lactic acidosis, participates in the reduction of cardiac contractility and in the vascular hyporesponsiveness to vasopressors through various mechanisms. However, the contributions of each mechanism responsible for these deleterious effects have not been fully determined and their respective consequences on organ failure are still poorly defined, particularly in humans. Despite some convincing experimental data, no clinical trial has established the level at which pH becomes deleterious for hemodynamics. Consequently, the essential treatment for lactic acidosis in shock patients is to correct the cause. It is unknown, however, whether symptomatic pH correction is beneficial in shock patients. The latest Surviving Sepsis Campaign guidelines recommend against the use of buffer therapy with pH ≥7.15 and issue no recommendation for pH levels <7.15. Furthermore, based on strong experimental and clinical evidence, sodium bicarbonate infusion alone is not recommended for restoring pH. Indeed, bicarbonate induces carbon dioxide generation and hypocalcemia, both cardiovascular depressant factors. This review addresses the principal hemodynamic consequences of shock-associated lactic acidosis. Despite the lack of formal evidence, this review also highlights the various adapted supportive therapy options that could be putatively added to causal treatment in attempting to reverse the hemodynamic consequences of shock-associated lactic acidosis.
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Affiliation(s)
- Antoine Kimmoun
- CHU Nancy, Service de Réanimation Médicale Brabois, Pole Cardiovasculaire et Réanimation Médicale, Hôpital de Brabois, Vandoeuvre-les-Nancy, 54511, France. .,Université de Lorraine, Nancy, 54000, France. .,INSERM U1116, Groupe Choc, Faculté de Médecine, Vandoeuvre-les-Nancy, 54511, France.
| | - Emmanuel Novy
- CHU Nancy, Service de Réanimation Médicale Brabois, Pole Cardiovasculaire et Réanimation Médicale, Hôpital de Brabois, Vandoeuvre-les-Nancy, 54511, France. .,Université de Lorraine, Nancy, 54000, France.
| | - Thomas Auchet
- CHU Nancy, Service de Réanimation Médicale Brabois, Pole Cardiovasculaire et Réanimation Médicale, Hôpital de Brabois, Vandoeuvre-les-Nancy, 54511, France.
| | - Nicolas Ducrocq
- CHU Nancy, Service de Réanimation Médicale Brabois, Pole Cardiovasculaire et Réanimation Médicale, Hôpital de Brabois, Vandoeuvre-les-Nancy, 54511, France.
| | - Bruno Levy
- CHU Nancy, Service de Réanimation Médicale Brabois, Pole Cardiovasculaire et Réanimation Médicale, Hôpital de Brabois, Vandoeuvre-les-Nancy, 54511, France. .,Université de Lorraine, Nancy, 54000, France. .,INSERM U1116, Groupe Choc, Faculté de Médecine, Vandoeuvre-les-Nancy, 54511, France.
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Propofol increases morbidity and mortality in a rat model of sepsis. CRITICAL CARE : THE OFFICIAL JOURNAL OF THE CRITICAL CARE FORUM 2015; 19:45. [PMID: 25887642 PMCID: PMC4344774 DOI: 10.1186/s13054-015-0751-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 01/16/2015] [Indexed: 01/20/2023]
Abstract
INTRODUCTION Severe sepsis is associated with approximately 50% mortality and accounts for tremendous healthcare costs. Most patients require ventilatory support and propofol is commonly used to sedate mechanically ventilated patients. Volatile anesthetics have been shown to attenuate inflammation in a variety of different settings. We therefore hypothesized that volatile anesthetic agents may offer beneficial immunomodulatory effects during the course of long-term intra-abdominal sepsis in rats under continuous sedation and ventilation for up to 24 hours. METHODS Sham operation or cecal ligation and puncture (CLP) was performed in adult male Wistar rats followed by mechanical ventilation. Animals were sedated for 24 hours with propofol (7 to 20 mg/kg/h), sevoflurane, desflurane or isoflurane (0.7 minimal alveolar concentration each). RESULTS Septic animals sedated with propofol showed a mean survival time of 12 hours, whereas >56% of all animals in the volatile groups survived 24 hours (P <0.001). After 18 hours, base excess in propofol + CLP animals (-20.6 ± 2.0) was lower than in the volatile groups (isoflurane + CLP: -11.7 ± 4.2, sevoflurane + CLP: -11.8 ± 3.5, desflurane + CLP -14.2 ± 3.7; all P <0.03). Plasma endotoxin levels reached 2-fold higher levels in propofol + CLP compared to isoflurane + CLP animals at 12 hours (P <0.001). Also blood levels of inflammatory mediators (tumor necrosis factor-α, interleukin-1β, interleukin-10, CXCL-2, interferon-γ and high mobility group protein-1) were accentuated in propofol + CLP rats compared to the isoflurane + CLP group at the same time point (P <0.04). CONCLUSIONS This is the first study to assess prolonged effects of sepsis and long-term application of volatile sedatives compared to propofol on survival, cardiovascular, inflammatory and end organ parameters. Results indicate that volatile anesthetics dramatically improved survival and attenuate systemic inflammation as compared to propofol. The main mechanism responsible for adverse propofol effects could be an enhanced plasma endotoxin concentration, leading to profound hypotension, which was unresponsive to fluid resuscitation.
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Cabrera CP, Ng FL, Warren HR, Barnes MR, Munroe PB, Caulfield MJ. Exploring hypertension genome-wide association studies findings and impact on pathophysiology, pathways, and pharmacogenetics. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2015; 7:73-90. [DOI: 10.1002/wsbm.1290] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2014] [Revised: 11/25/2014] [Accepted: 01/05/2015] [Indexed: 01/11/2023]
Affiliation(s)
- Claudia P Cabrera
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London UK
- NIHR Barts Cardiovascular Biomedical Research Unit; Queen Mary University of London; London UK
| | - Fu Liang Ng
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London UK
| | - Helen R Warren
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London UK
- NIHR Barts Cardiovascular Biomedical Research Unit; Queen Mary University of London; London UK
| | - Michael R Barnes
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London UK
- NIHR Barts Cardiovascular Biomedical Research Unit; Queen Mary University of London; London UK
| | - Patricia B Munroe
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London UK
- NIHR Barts Cardiovascular Biomedical Research Unit; Queen Mary University of London; London UK
| | - Mark J Caulfield
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry; Queen Mary University of London; London UK
- NIHR Barts Cardiovascular Biomedical Research Unit; Queen Mary University of London; London UK
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Girault A, Brochiero E. Evidence of K+ channel function in epithelial cell migration, proliferation, and repair. Am J Physiol Cell Physiol 2013; 306:C307-19. [PMID: 24196531 DOI: 10.1152/ajpcell.00226.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Efficient repair of epithelial tissue, which is frequently exposed to insults, is necessary to maintain its functional integrity. It is therefore necessary to better understand the biological and molecular determinants of tissue regeneration and to develop new strategies to promote epithelial repair. Interestingly, a growing body of evidence indicates that many members of the large and widely expressed family of K(+) channels are involved in regulation of cell migration and proliferation, key processes of epithelial repair. First, we briefly summarize the complex mechanisms, including cell migration, proliferation, and differentiation, engaged after epithelial injury. We then present evidence implicating K(+) channels in the regulation of these key repair processes. We also describe the mechanisms whereby K(+) channels may control epithelial repair processes. In particular, changes in membrane potential, K(+) concentration, cell volume, intracellular Ca(2+), and signaling pathways following modulation of K(+) channel activity, as well as physical interaction of K(+) channels with the cytoskeleton or integrins are presented. Finally, we discuss the challenges to efficient, specific, and safe targeting of K(+) channels for therapeutic applications to improve epithelial repair in vivo.
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Affiliation(s)
- Alban Girault
- Centre de Recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), Montreal, Quebec, Canada; and
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AMPA receptor pHluorin-GluA2 reports NMDA receptor-induced intracellular acidification in hippocampal neurons. Proc Natl Acad Sci U S A 2013; 110:14426-31. [PMID: 23940334 DOI: 10.1073/pnas.1312982110] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
NMDA receptor activation promotes endocytosis of AMPA receptors, which is an important mechanism underlying long-term synaptic depression. The pH-sensitive GFP variant pHluorin fused to the N terminus of GluA2 (pH-GluA2) has been used to assay NMDA-mediated AMPA receptor endocytosis and recycling. Here, we demonstrate that in somatic and dendritic regions of hippocampal neurons a large fraction of the fluorescent signal originates from intracellular pH-GluA2, and that the decline in fluorescence in response to NMDA and AMPA primarily describes an intracellular acidification, which quenches the pHluorin signal from intracellular receptor pools. Neurons expressing an endoplasmic reticulum-retained mutant of GluA2 (pH-GluA2 ΔC49) displayed a larger response to NMDA than neurons expressing wild-type pH-GluA2. A similar NMDA-elicited decline in pHluorin signal was observed by expressing cytosolic pHluorin alone without fusion to GluA2 (cyto-pHluorin). Intracellular acidification in response to NMDA was further confirmed by using the ratiometric pH indicator carboxy-SNARF-1. The NMDA-induced decline was followed by rapid recovery of the fluorescent signal from both cyto-pHluorin and pH-GluA2. The recovery was sodium-dependent and sensitive to Na(+)/H(+)-exchanger (NHE) inhibitors. Moreover, recovery was more rapid after shRNA-mediated knockdown of the GluA2 binding PDZ domain-containing protein interacting with C kinase 1 (PICK1). Interestingly, the accelerating effect of PICK1 knockdown on the fluorescence recovery was eliminated in the presence of the NHE1 inhibitor zoniporide. Our results indicate that the pH-GluA2 recycling assay is an unreliable assay for studying AMPA receptor trafficking and also suggest a role for PICK1 in regulating intracellular pH via modulation of NHE activity.
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Dabertrand F, Nelson MT, Brayden JE. Ryanodine receptors, calcium signaling, and regulation of vascular tone in the cerebral parenchymal microcirculation. Microcirculation 2013; 20:307-16. [PMID: 23216877 PMCID: PMC3612564 DOI: 10.1111/micc.12027] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2012] [Accepted: 11/21/2012] [Indexed: 11/27/2022]
Abstract
The cerebral blood supply is delivered by a surface network of pial arteries and arterioles from which arise (parenchymal) arterioles that penetrate into the cortex and terminate in a rich capillary bed. The critical regulation of CBF, locally and globally, requires precise vasomotor regulation of the intracerebral microvasculature. This vascular region is anatomically unique as illustrated by the presence of astrocytic processes that envelope almost the entire basolateral surface of PAs. There are, moreover, notable functional differences between pial arteries and PAs. For example, in pial VSMCs, local calcium release events ("calcium sparks") through ryanodine receptor (RyR) channels in SR membrane activate large conductance, calcium-sensitive potassium channels to modulate vascular diameter. In contrast, VSMCs in PAs express functional RyR and BK channels, but under physiological conditions, these channels do not oppose pressure-induced vasoconstriction. Here, we summarize the roles of ryanodine receptors in the parenchymal microvasculature under physiologic and pathologic conditions, and discuss their importance in the control of CBF.
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Affiliation(s)
- Fabrice Dabertrand
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont, USA.
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18
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Boedtkjer E, Aalkjaer C. Intracellular pH in the resistance vasculature: regulation and functional implications. J Vasc Res 2012; 49:479-96. [PMID: 22907294 DOI: 10.1159/000341235] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/20/2012] [Indexed: 12/18/2022] Open
Abstract
Net acid extrusion from vascular smooth muscle (VSMCs) and endothelial cells (ECs) in the wall of resistance arteries is mediated by the Na(+),HCO(3)(-) cotransporter NBCn1 (SLC4A7) and the Na(+)/H(+) exchanger NHE1 (SLC9A1) and is essential for intracellular pH (pH(i)) control. Experimental evidence suggests that the pH(i) of VSMCs and ECs modulates both vasocontractile and vasodilatory functions in resistance arteries with implications for blood pressure regulation. The connection between disturbed pH(i) and altered cardiovascular function has been substantiated by a genome-wide association study showing a link between NBCn1 and human hypertension. On this basis, we here review the current evidence regarding (a) molecular mechanisms involved in pH(i) control in VSMCs and ECs of resistance arteries at rest and during contractions, (b) implications of disturbed pH(i) for resistance artery function, and (c) involvement of disturbed pH(i) in the pathogenesis of vascular disease. The current evidence clearly implies that pH(i) of VSMCs and ECs modulates vascular function and suggests that disturbed pH(i) either consequent to disturbed regulation or due to metabolic challenges needs to be taken into consideration as a mechanistic component of artery dysfunction and disturbed blood pressure regulation.
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Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine and Water and Salt Research Center, Aarhus University, Aarhus, Denmark.
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Liang GH, Xi Q, Leffler CW, Jaggar JH. Hydrogen sulfide activates Ca²⁺ sparks to induce cerebral arteriole dilatation. J Physiol 2012; 590:2709-20. [PMID: 22508960 DOI: 10.1113/jphysiol.2011.225128] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Hydrogen sulfide (H₂S) is a gaseous vasodilator produced by endothelial cells. Mechanisms by which H₂S induces vasodilatation are unclear. We tested the hypothesis that H₂S dilates cerebral arterioles by modulating local and global intracellular Ca²⁺ signals in smooth muscle cells. High-speed confocal imaging revealed that Na₂S, an H₂S donor, increased Ca²⁺ spark frequency ∼1.43-fold and decreased global intracellular Ca²⁺ concentration ([Ca²⁺]i) by ∼37 nM in smooth muscle cells of intact piglet cerebral arterioles. In contrast, H₂S did not alter Ca²⁺ wave frequency. In voltage-clamped (-40 mV) cells, H₂S increased the frequency of iberiotoxin-sensitive, Ca²⁺ spark-induced transient Ca²⁺-activated K⁺ (KCa) currents ∼1.83-fold, but did not alter the amplitude of these events. H₂S did not alter the activity of single KCa channels recorded in the absence of Ca²⁺ sparks in arteriole smooth muscle cells. H₂S increased SR Ca²⁺ load ([Ca²⁺]SR), measured as caffeine (10 and 20mM)-induced [Ca²⁺]i transients, ∼1.5-fold. H₂S hyperpolarized (by ∼18 mV) and dilated pressurized (40 mmHg) cerebral arterioles. Iberiotoxin, a KCa channel blocker, reduced H₂S-induced hyperpolarization by ∼51%. Iberiotoxin and ryanodine, a ryanodine receptor channel inhibitor, reduced H₂S-induced vasodilatation by ∼38 and ∼37%, respectively. In summary, our data indicate that H₂S elevates [Ca²⁺]SR, leading to Ca²⁺ spark activation in cerebral arteriole smooth muscle cells. The subsequent elevation in transient KCa current frequency leads to membrane hyperpolarization, a reduction in global [Ca²⁺]i and vasodilatation.
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Affiliation(s)
- Guo Hua Liang
- Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA
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Crimi E, Taccone FS, Infante T, Scolletta S, Crudele V, Napoli C. Effects of intracellular acidosis on endothelial function: an overview. J Crit Care 2011; 27:108-18. [PMID: 21798701 DOI: 10.1016/j.jcrc.2011.06.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2011] [Revised: 05/17/2011] [Accepted: 06/03/2011] [Indexed: 01/13/2023]
Abstract
The endothelium represents the largest functional organ in the human body playing an active role in vasoregulation, coagulation, inflammation, and microvascular permeability. Endothelium contributes to maintain vascular integrity, intravascular volume, and tissue oxygenation promoting inflammatory network response for local defense and repair. Acid-basis homeostasis is an important physiologic parameter that controls cell function, and changes in pH can influence vascular tone by regulating endothelium and vascular smooth muscle cells. This review presents a current perspective of the effects of intracellular acidosis on the function and the basic regulatory mechanisms of endothelial cells.
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Affiliation(s)
- Ettore Crimi
- Department of Anesthesia and Critical Care Medicine, Shands Hospital, University of Florida, Gainesville, FL 32608, USA
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Celotto AC, Restini CBA, Capellini VK, Bendhack LM, Evora PRB. Acidosis induces relaxation mediated by nitric oxide and potassium channels in rat thoracic aorta. Eur J Pharmacol 2011; 656:88-93. [PMID: 21300058 DOI: 10.1016/j.ejphar.2011.01.053] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 01/05/2011] [Accepted: 01/25/2011] [Indexed: 10/18/2022]
Abstract
We investigated the mechanism by which extracellular acidification promotes relaxation in rat thoracic aorta. The relaxation response to HCl-induced extracellular acidification (7.4 to 6.5) was measured in aortic rings pre-contracted with phenylephrine (Phe, 10(-6) M) or KCl (45mM). The vascular reactivity experiments were performed in endothelium-intact and denuded rings, in the presence or absence of indomethacin (10(-5) M), L-NAME (10(-4) M), apamin (10(-6) M), and glibenclamide (10(-5) M). The effect of extracellular acidosis (pH 7.0 and 6.5) on nitric oxide (NO) production was evaluated in isolated endothelial cells loaded with diaminofluorescein-FM diacetate (DAF-FM DA, 5μM). The extracellular acidosis failed to induce any changes in the vascular tone of aortic rings pre-contracted with KCl, however, it caused endothelium-dependent and independent relaxation in rings pre-contracted with Phe. This acidosis induced-relaxation was inhibited by L-NAME, apamin, and glibenclamide, but not by indomethacin. The acidosis (pH 7.0 and 6.5) also promoted a time-dependent increase in the NO production by the isolated endothelial cells. These results suggest that extracellular acidosis promotes vasodilation mediated by NO, K(ATP) and SK(Ca), and maybe other K(+) channels in isolated rat thoracic aorta.
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Affiliation(s)
- Andréa C Celotto
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
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Li Y, Horiuchi T, Murata T, Hongo K. Mechanism of alkalosis-induced constriction of rat cerebral penetrating arterioles. Neurosci Res 2011; 70:98-103. [PMID: 21256899 DOI: 10.1016/j.neures.2011.01.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2010] [Revised: 12/22/2010] [Accepted: 01/11/2011] [Indexed: 10/18/2022]
Abstract
Cerebral arterioles are in close contact with the supplied tissue and are strong regulators of cerebrovascular tone. Transient ischemia can cause brain intracellular alkalosis producing vasoconstriction. However, the mechanisms of alkalosis-induced cerebral arteriolar constriction are poorly understood. Here, we determined the vascular responses to alkalosis under different conditions by monitoring the internal diameter of pressurized penetrating arterioles isolated from the rat cerebrum with an operating microscope. The roles of Na+/H+ exchanger (NHE), Na+/Ca²+ exchanger (NCX), Na+/K+-adenosine triphosphatase (NKA), and potassium (K+) channels during alkalosis were examined using specific inhibitors. Our results indicated that the extent of constriction of the penetrating arterioles was dependent on alkaline pH. Moreover, the alkalosis-induced vasoconstriction was significantly attenuated by inhibitors of NHE, NCX, and NKA, but not K+ channel inhibitors. Therefore, we concluded that NHE, NKA, and NCX are important regulators involved in alkalosis-induced vasoconstriction of rat cerebral penetrating arterioles.
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Affiliation(s)
- Yuhui Li
- Department of Neurosurgery, Shinshu University School of Medicine, Asahi 3-1-1, Matsumoto 390-8621, Japan
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Celotto AC, Capellini VK, Restini CBA, Baldo CF, Bendhack LM, Evora PRB. Extracellular alkalinization induces endothelium-derived nitric oxide dependent relaxation in rat thoracic aorta. Nitric Oxide 2010; 23:269-74. [PMID: 20682356 DOI: 10.1016/j.niox.2010.07.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2010] [Revised: 07/10/2010] [Accepted: 07/29/2010] [Indexed: 10/19/2022]
Abstract
AIM To investigate the mechanism through which the extracellular alkalinization promotes relaxation in rat thoracic aorta. METHODS The relaxation response to NaOH-induced extracellular alkalinization (7.4-8.5) was measured in aortic rings pre-contracted with phenylephrine (Phe, 10(-6) M). The vascular reactivity experiments were performed in endothelium-intact and -denuded rings, in the presence or and absence of indomethacin (10(-5) M), NG-nitro-l-arginine methyl ester (L-NAME, 10(-4) M), N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide/HCl (W-7, 10(-7) M), 2,5-dimethylbenzimidazole (DMB, 2×10(-5) M) and methyl-β-cyclodextrin (10(-2) M). In addition, the effects of NaOH-induced extracellular alkalinization (pH 8.0 and 8.5) on the intracellular nitric oxide (NO) concentration was evaluated in isolated endothelial cells loaded with diaminofluorescein-FM diacetate (DAF-FM DA, 5 μM), in the presence and absence of DMB (2×10(-5) M). RESULTS The extracellular alkalinization failed to induce any change in vascular tone in aortic rings pre-contracted with KCl. In rings pre-contracted with Phe, the extracellular alkalinization caused relaxation in the endothelium-intact rings only, and this relaxation was maintained after cyclooxygenase inhibition; completely abolished by the inhibition of nitric oxide synthase (NOS), Ca(2+)/calmodulin and Na(+)/Ca(2+) exchanger (NCX), and partially blunted by the caveolae disassembly. CONCLUSIONS These results suggest that, in rat thoracic aorta, that extracellular alkalinization with NaOH activates the NCX reverse mode of endothelial cells in rat thoracic aorta, thereby the intracellular Ca(2+) concentration and activating the Ca(2+)/calmodulin-dependent NOS. In turn, NO is released promoting relaxation.
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Affiliation(s)
- A C Celotto
- Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil
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Ozaslan M, Zumrutdal ME, Daglioglu K, Kilic IH, Karagoz ID, Kalender M, Tuzcu M, Colak O, Cengiz B. Antitumoral Effect of L. inermis in Mice with EAC. INT J PHARMACOL 2009. [DOI: 10.3923/ijp.2009.263.267] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Cheng YM, Kelly T, Church J. Potential contribution of a voltage-activated proton conductance to acid extrusion from rat hippocampal neurons. Neuroscience 2007; 151:1084-98. [PMID: 18201832 DOI: 10.1016/j.neuroscience.2007.12.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Revised: 11/23/2007] [Accepted: 12/07/2007] [Indexed: 11/27/2022]
Abstract
We examined the potential contribution of a voltage-gated proton conductance (gH+) to acid extrusion from cultured postnatal rat hippocampal neurons. In neurons loaded with Ca2+- and/or pH-sensitive fluorophores, transient exposures to 25-139.5 mM external K+ (K+o) or 20 microM veratridine in the presence of 2 mM Ca2+o (extracellular pH (pHo) constant at 7.35) caused reversible increases and decreases in intracellular free calcium concentration ([Ca2+]i) and intracellular pH (pHi), respectively. In contrast, under external Ca2+-free conditions, the same stimuli failed to affect [Ca2+]i but caused an increase in pHi, the magnitude of which was related to the [K+]o applied and the change in membrane potential. Consistent with the properties of gH+s in other cell types, the magnitude of the rise in pHi observed in the absence of external Ca2+ was not affected by the removal of external Na+ but was sensitive to external Zn2+ and temperature and was dependent on the measured transmembrane pH gradient (DeltapHmemb). Increasing DeltapH(memb) by pretreatment with carbonylcyanide-p-trifluoromethoxyphenylhydrazone augmented both the high-[K+]o-evoked rise in pHi and the Zn2+-sensitive component of the rise in pHi, suggestive of increased acid extrusion via a gH+. The inhibitory effect of Zn2+ at a given DeltapHmemb was further enhanced by increasing pHo from 7.35-7.8, consistent with a pHo-dependent inhibition of the putative gH+ by Zn2+. Under conditions designed to isolate H+ currents, a voltage-dependent outward current was recorded from whole-cell patch-clamped neurons. Although the outward current appeared to show some selectivity for protons, it was not sensitive to Zn2+ or temperature and the H+-selective component could not be separated from a larger conductance of unknown selectivity. Nonetheless, taken together, the results suggest that a Zn2+-sensitive proton conductive pathway is present in rat hippocampal neurons and contributes to H+ efflux under depolarizing conditions.
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Affiliation(s)
- Y M Cheng
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
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Park JK, Kim YC, Sim JH, Choi MY, Choi W, Hwang KK, Cho MC, Kim KW, Lim SW, Lee SJ. Regulation of membrane excitability by intracellular pH (pHi) changers through Ca2+-activated K+ current (BK channel) in single smooth muscle cells from rabbit basilar artery. Pflugers Arch 2007; 454:307-19. [PMID: 17285302 DOI: 10.1007/s00424-007-0204-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Accepted: 12/31/2006] [Indexed: 01/12/2023]
Abstract
Employing microfluorometric system and patch clamp technique in rabbit basilar arterial myocytes, regulation mechanisms of vascular excitability were investigated by applying intracellular pH (pH(i)) changers such as sodium acetate (SA) and NH(4)Cl. Applications of caffeine produced transient phasic contractions in a reversible manner. These caffeine-induced contractions were significantly enhanced by SA and suppressed by NH(4)Cl. Intracellular Ca(2+) concentration ([Ca(2+)](i)) was monitored in a single isolated myocyte and based the ratio of fluorescence using Fura-2 AM (R (340/380)). SA (20 mM) increased and NH(4)Cl (20 mM) decreased R (340/380) by 0.2 +/- 0.03 and 0.1 +/- 0.02, respectively, in a reversible manner. Caffeine (10 mM) transiently increased R (340/380) by 0.9 +/- 0.07, and the ratio increment was significantly enhanced by SA and suppressed by NH(4)Cl, implying that SA and NH(4)Cl may affect [Ca(2+)](i) (p < 0.05). Accordingly, we studied the effects of SA and NH(4)Cl on Ca(2+)-activated K(+) current (IK(Ca)) under patch clamp technique. Caffeine produced transient outward current at holding potential (V (h)) of 0 mV, caffeine induced transient outward K(+) current, and the spontaneous transient outward currents were significantly enhanced by SA and suppressed by NH(4)Cl. In addition, IK(Ca) was significantly increased by acidotic condition when pH(i) was lowered by altering the NH(4)Cl gradient across the cell membrane. Finally, the effects of SA and NH(4)Cl on the membrane excitability and basal tension were studied: Under current clamp mode, resting membrane potential (RMP) was -28 +/- 2.3 mV in a single cell level and was depolarized by 13 +/- 2.4 mV with 2 mM tetraethylammonium (TEA). SA hyperpolarized and NH(4)Cl depolarized RMP by 10 +/- 1.9 and 16 +/- 4.7 mV, respectively. SA-induced hyperpolarization and relaxation of basal tension was significantly inhibited by TEA. These results suggest that SA and NH(4)Cl might regulate vascular tone by altering membrane excitability through modulation of [Ca(2+)](i) and Ca(2+)-activated K channels in rabbit basilar artery.
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Affiliation(s)
- Jong Kook Park
- Department of Anesthesiology and Pain Medicine, College of Medicine, Cheju National University, 66 Jejudaehakno, Jeju, Jeju Special Self-Governing Province 690-756, South Korea
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28
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Liu G, Daneshgari F. Effects of cold storage on the function and morphology of isolated urinary bladder in rat. Neurourol Urodyn 2006; 25:381-7. [PMID: 16710851 DOI: 10.1002/nau.20169] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
AIMS We investigated the effects of 24- and 48-hr storage at 4 degrees C in Krebs solution on the function and morphology of isolated, rat urinary bladders. METHODS Strips of bladder were obtained from eight male Sprague-Dawley rats. Six strips were harvested from each bladder and randomized to storage for 24 or 48 hr at 4 degrees C in Krebs solution or examination immediately after harvest. Contractile responses of the strips to potassium chloride (KCl), electric field stimulation (EFS), adenosine 5'-triphosphate (ATP) and carbamylcholine (CCh) were assessed. Histological examination of the bladder strips was performed. The pO(2), pCO(2), and pH of the solution in each storage container were measured at each storage time point. RESULTS Cold storage induced a significant decrease in the amplitude of contraction in response to KCl and EFS after 24 or 48 hr of storage compared with control. The response of the bladder strips to ATP and CCh was significantly reduced after 48-hr storage compared with control, but not 24-hr storage. The pO(2) and pCO(2) decreased after cold storage. The pH increased after 24 hr of storage and remained stable between 24 and 48 hr of storage. Histological evaluation of the strips showed tissue swelling after 24 and 48 hr of storage. CONCLUSIONS These results suggest that the morphology and function of bladder strips stored for 24 to 48 hr at 4 degrees C in Krebs solution undergo significant changes. Further studies are needed to assess the allowable time for storage of bladder tissue.
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Affiliation(s)
- Guiming Liu
- Glickman Urological Institute and Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
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Wakabayashi I, Poteser M, Groschner K. Intracellular pH as a determinant of vascular smooth muscle function. J Vasc Res 2006; 43:238-50. [PMID: 16449818 DOI: 10.1159/000091235] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2005] [Accepted: 11/20/2005] [Indexed: 11/19/2022] Open
Abstract
Intracellular pH (pHi) is a physiological parameter that is intimately linked to contractility, growth and proliferation of vascular smooth muscle (VSM). Regarding contractility, no general unifying concept of pHi regulation but a rather complex relation between pHi signals and vascular tone has been revealed so far. The modulation of vasotone by pHi depends on the type of blood vessel as well as on the pattern of regulatory input signals. In addition, changes in pHi have been recognized as an important cellular signal to determine the fate of cells in terms of proliferation or apoptosis. Cellular sensors for pHi include a variety of ion transport systems which control intracellular Ca2+ gradients and are likely to serve as a link between pHi and cell functions. Here we provide an overview on the potential targets and mechanisms that transduce pHi signals in VSM. The role of pHi-sensing signaling complexes and localized pHi signaling as the basis of diversity of pHi regulation of VSM function is discussed.
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Affiliation(s)
- Ichiro Wakabayashi
- Department of Hygiene and Preventive Medicine, Yamagata University School of Medicine, Yamagata, Japan.
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30
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Sarosi GA, Jaiswal K, Herndon E, Lopez-Guzman C, Spechler SJ, Souza RF. Acid increases MAPK-mediated proliferation in Barrett's esophageal adenocarcinoma cells via intracellular acidification through a Cl-/HCO3- exchanger. Am J Physiol Gastrointest Liver Physiol 2005; 289:G991-7. [PMID: 16081761 DOI: 10.1152/ajpgi.00215.2005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Abundant epidemiological evidence links acid reflux to adenocarcinoma in Barrett's esophagus, but few studies have examined the cellular mechanisms by which acid promotes this neoplastic progression. We hypothesized that extracellular acid exposure causes intracellular acidification that triggers MAPK signaling and proliferation in Barrett's epithelial cells. We tested that hypothesis in a Barrett's-derived esophageal adenocarcinoma cell line (SEG-1). SEG-1 cells were exposed to varying concentrations of acid, and intracellular pH (pH(i)) was measured by 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein microfluorimetry. After acid exposure, ERK and p38 MAPK activation were measured by Western blot analysis and an immune complex kinase assay. Proliferation was measured by Coulter counter cell counts and a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide incorporation assay. Exposure of SEG-1 cells to solutions with a pH between 3 and 6.5 caused a rapid, reversible decrease in pH(i) to a level approximately equal to extracellular pH. Acid exposure caused a rapid activation of both ERK and p38 MAPKs and also resulted in pH-dependent increases in cell number, with a maximum increase of 41% observed at pH 6.0. The MAPK activation and proliferation in SEG-1 cells induced by acid exposure could be blocked by pretreatment with disodium 4,4'-diisothiocyanatostilbine-2,2'-disulfonate (DIDS), which prevents intracellular acidification by inhibiting the Cl(-)/HCO(3)(-) exchanger. In conclusion, in SEG-1 cells, extracellular acid exposure causes intracellular acidification, which activates MAPK and causes proliferation. The magnitude of these effects is pH dependent, and the effects can be inhibited by preventing intracellular acidification with DIDS.
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Affiliation(s)
- George A Sarosi
- Dept. of Surgery, Medical University of Texas Southwestern Medical Center, Dallas, TX 75216, USA
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31
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Muneer A, Cellek S, Dogan A, Kell PD, Ralph DJ, Minhas S. Investigation of cavernosal smooth muscle dysfunction in low flow priapism using an in vitro model. Int J Impot Res 2005; 17:10-8. [PMID: 15071490 DOI: 10.1038/sj.ijir.3901231] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The effects of hypoxia (pO2: 50 mmHg), acidosis (pH: 6.9) or glucopenia (absence of glucose) in vitro on the tone of the rabbit corpus cavernosum were investigated. The recovery of smooth muscle contractility following exposure to these conditions was also assessed. Hypoxia, acidosis or glucopenia alone or in combination showed a sustained reduction in the tone. Reperfusion of tissue strips showed complete recovery of smooth muscle tone for all conditions except when hypoxia and glucopenia were combined or when hypoxia, glucopenia and acidosis were used in combination. Incomplete recovery of tone was associated with a significant reduction in tissue ATP concentrations and an increase in the number of TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling)-positive nuclei. This indicates that following reversal of hypoxia, acidosis and glucopenia, failure of conventional alpha-adrenergic agonists to produce tumescence in low flow priapism is associated with irreversible smooth muscle cell dysfunction, which is linked to ATP reduction and smooth muscle cell death.
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Affiliation(s)
- A Muneer
- The St Peter's Andrology Centre, University College London, London, UK
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32
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Horai Y, Furukawa KI, Iwata S, Ohizumi Y. Changes in pH Increase Perfusion Pressure of Coronary Arteries in the Rat. J Pharmacol Sci 2005; 97:400-7. [PMID: 15750285 DOI: 10.1254/jphs.fp0040669] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Stricture of coronary arteries is closely related to ischemic heart disease. The purpose of this study was to examine whether changes in pH caused contraction of rat coronary arteries, as determined using Langendorff perfused hearts. Changing the pH of the perfusate increased perfusion pressure as an indication of the contractile state of coronary arteries. Alkaline pH-induced increase of perfusion pressure in Wistar Kyoto rats (WKY) was almost identical to that of spontaneously hypertensive rats (SHR), whereas acidic pH-induced increase in SHR was much greater than that in WKY. Acidic pH-induced increase in perfusion pressure was inhibited by verapamil, cromakalim, and adenosine. Feeding WKY with N(G)-nitro-L-arginine resulted in hypertension followed by enhanced acidic pH-induced increase in perfusion pressure. These results suggest that acidic-pH induced contraction of rat coronary arteries is caused by Ca(2+) influx through voltage-dependent Ca(2+) channels and the contraction is enhanced by hypertension.
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Affiliation(s)
- Yasushi Horai
- Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai
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Hyvelin JM, O'Connor C, McLoughlin P. Effect of changes in pH on wall tension in isolated rat pulmonary artery: role of the RhoA/Rho-kinase pathway. Am J Physiol Lung Cell Mol Physiol 2004; 287:L673-84. [PMID: 14766667 DOI: 10.1152/ajplung.00331.2003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary arteries (PA) are resistant to the vasodilator effects of extracellular acidosis in systemic vessels; the mechanism underlying this difference between systemic and pulmonary circulations has not been elucidated. We hypothesized that RhoA/Rho-kinase-mediated Ca2+ sensitization pathway played a greater role in tension development in pulmonary than in systemic vascular smooth muscle and that this pathway was insensitive to acidosis. In arterial rings contracted with the alpha1-agonist phenylephrine (PE), the Rho-kinase inhibitor Y-27632 (< or =3 microM) induced greater relaxation in precontracted PA rings than in aortic rings. In PA rings stimulated by PE, the activation of RhoA was greater than in aorta. Normocapnic acidosis (NA) induced a smaller relaxation in precontracted PA than in aorta. However, in the presence of nifedipine and thapsigargin, when PE-induced contraction was predominantly mediated by Rho-kinase, the relaxant effect of NA was reduced and similar in both vessel types. Furthermore, in the presence of Y-27632, NA induced a greater relaxation in both PA and aorta, which was similar in both vessels. Finally, in alpha-toxin-permeabilized smooth muscle, PE-induced contraction at constant Ca2+ activity was inhibited by Y-27632 and unaffected by acidosis. These results indicate that Ca2+ sensitization induced by the RhoA/Rho-kinase pathway played a greater role in agonist-induced vascular smooth muscle contraction in PA than in aorta and that tension mediated by this pathway was insensitive to acidosis. The predominant role of the RhoA/Rho-kinase pathway in the pulmonary vasculature may account for the resistance of this circulation to the vasodilator effect of acidosis observed in the systemic circulation.
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Affiliation(s)
- Jean-Marc Hyvelin
- Department of Physiology, Conway Institute of Biomolecular and Biomedical Research, Dublin 2, Ireland
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Weirich J, Dumont L, Fleckenstein-Grün G. Contribution of store-operated Ca2+ entry to pHo-dependent changes in vascular tone of porcine coronary smooth muscle. Cell Calcium 2004; 35:9-20. [PMID: 14670367 DOI: 10.1016/s0143-4160(03)00156-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Vascular smooth muscle contracts on increases of extracellular pH (pH(o)) and relaxes on pH(o) decreases possibly resulting from changes in transsarcolemmal Ca(2+) influx. Therefore, we studied store-operated Ca(2+) entry (SOCE; i.e. capacitative Ca(2+) entry (CCE)) during acidification (pH(o)=6.5) and alkalinization (pH(o)=8.0) in isolated porcine coronary smooth muscle cells (SMCs) by monitoring cytoplasmic Ca(2+) ([Ca(2+)](i)) and divalent cation entry (Mn(2+) quench) with fura-2/AM-fluorometry. Additionally, we evaluated the contribution of SOCE to pH(o)-dependent changes in isometric tension of porcine coronary smooth muscle strips. SOCE elicited in SMCs by the SERCA inhibitor BHQ was strongly modulated by pH(o) showing a decrease upon acidification and vice versa an increase upon alkalinization. BHQ-mediated tension of smooth muscle strips also revealed strong pH(o) dependence. In contrast, L-VOC-dependent tension ([K(+)](o)=20 and 40 mmol l(-1)) was remarkably less affected by pH(o) changes. Moreover, refilling of depleted Ca(2+) stores after repeated M(3)-cholinergic receptor stimulation could be almost completely inhibited by SKF 96365 and was markedly reduced by acidification and considerably enhanced by alkalinization pointing to a major role of SOCE in refilling. We conclude that vascular tone particularly responds to alterations in pH(o) whenever SOCE substantially contributes to the amount of activator Ca(2+) for contraction.
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Affiliation(s)
- Jörg Weirich
- Department of Physiology, University of Freiburg i. Br., Hermann-Herder-Strasse 7, D-79104 Freiburg, Germany
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35
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Susa S, Wakabayashi I. Extracellular alkalosis activates ERK mitogen-activated protein kinase of vascular smooth muscle cells through NADPH-mediated formation of reactive oxygen species. FEBS Lett 2003; 554:399-402. [PMID: 14623101 DOI: 10.1016/s0014-5793(03)01198-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Extracellular alkalosis induced phosphorylation of extracellular signal-regulated kinase (ERK) and enhanced serum-induced ERK phosphorylation in cultured rat aortic smooth muscle cells. While extracellular alkalinization increased verapamil-sensitive (45)Ca(2+) uptake into the cells, ERK phosphorylation induced by extracellular alkalosis was not affected by verapamil. On the other hand, probes for oxidant signaling, such as superoxide dismutase, 4,5-dihydroxy-1,3-benzene-disulfonic acid, a cell-permeable antioxidant, and diphenyliodonium, a NADPH oxidase inhibitor, inhibited extracellular alkalosis-induced phosphorylation of ERK. These results suggest that activation of ERK induced by extracellular alkalosis is not dependent on transplasmalemmal Ca(2+) entry but is caused by reactive oxygen species derived from an activation of NADPH oxidase.
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Affiliation(s)
- Shinji Susa
- Department of Hygiene and Preventive Medicine, Yamagata University School of Medicine, Iida-Nishi 2-2-2, Yamagata 990-9585, Japan
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36
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Lindauer U, Vogt J, Schuh-Hofer S, Dreier JP, Dirnagl U. Cerebrovascular vasodilation to extraluminal acidosis occurs via combined activation of ATP-sensitive and Ca2+-activated potassium channels. J Cereb Blood Flow Metab 2003; 23:1227-38. [PMID: 14526233 DOI: 10.1097/01.wcb.0000088764.02615.b7] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Albeit controversial, it has been suggested by several authors that nitric oxide (NO) serves as a permissive factor in the cerebral blood flow response to systemic hypercapnia. Potassium channels are important regulators of cerebrovascular tone and may be modulated by a basal perivascular NO level. To elucidate the functional targets of the proposed NO modulation during hypercapnia-induced vasodilation, the authors performed experiments in isolated, cannulated, and pressurized rat middle cerebral arteries (MCA). Extracellular pH was reduced from 7.4 to 7.0 in the extraluminal bath to induce NO dependent vasodilation. Acidosis increased vessel diameter by 35 +/- 10%. In separate experiments, ATP-sensitive potassium channels (KATP) were blocked by extraluminal application of glibenclamide (Glib), Ca2+-activated potassium channels (KCa) by tetraethylammonium (TEA), voltage-gated potassium channels (Kv) by 4-aminopyridine, and inward rectifier potassium channels (KIR) by BaCl2. Na+-K+-ATP-ase was inhibited by ouabain. Application of TEA slightly constricted the arteries at pH 7.4 and slightly but significantly attenuated the vasodilation to acidosis. Inhibition of the other potassium channels or Na+-K+-ATP-ase had no effect. Combined blockade of KATP and KCa channels further reduced resting diameter, and abolished acidosis induced vasodilation. The authors conclude that mainly KCa channels are active under resting conditions. KATP and KCa channels are responsible for vasodilation to acidosis. Activity of one of these potassium channel families is sufficient for vasodilation to acidosis, and only combined inhibition completely abolishes vasodilation. During NO synthase inhibition, dilation to the KATP channel opener pinacidil or the KCa channel opener NS1619 was attenuated or abolished, respectively. The authors suggest that a basal perivascular NO level is necessary for physiologic KATP and KCa channel function in rat MCA. Future studies have to elucidate whether this NO dependent effect on KATP and KCa channel function is a principle mechanism of NO induced modulation of cerebrovascular reactivity and whether the variability of findings in the literature concerning a modulatory role of NO can be explained by different levels of vascular NO/cGMP concentrations within the cerebrovascular tree.
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Affiliation(s)
- Ute Lindauer
- Experimental Neurology, Charité, Humboldt-Universität, Berlin, Germany.
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37
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Abstract
The clinical applicability of the experimental data discussed previously remains questionable, and results of clinical studies on chemoprevention in Barrett's esophagus are needed. The utility of selectively targeting acid exposure, ODC, and COX-2 is not clear, and elucidation of that role will be facilitated by a better understanding of the contribution of these factors in the development of Barrett's cancers. The insights already gained into the basic mechanisms of acid exposure, ODC, and COX-2 in the pathogenesis of Barrett's esophagus and esophageal adenocarcinoma hold promise for the development of future therapies aimed at these molecular targets and their signaling pathways. In preclinical studies, the ability of COX-2 selective NSAIDs and DFMO to inhibit carcinogenesis is encouraging. Results of well-designed, prospective clinical studies, however, are still needed to establish the efficacy of potent acid suppression, COX-2 inhibitors, and DFMO in the prevention of this malignancy.
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Affiliation(s)
- Rhonda F Souza
- Division of Gastroenterology, Dallas VA Medical Center, Dallas, TX 75216, USA.
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38
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Rohra DK, Saito SY, Ohizumi Y. Functional role of ryanodine-sensitive Ca2+ stores in acidic pH-induced contraction in Wistar Kyoto rat aorta. Life Sci 2003; 72:1259-69. [PMID: 12570926 DOI: 10.1016/s0024-3205(02)02370-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Acidic pH induced a contraction in the isolated aorta from Wistar Kyoto rat. The magnitude of contraction was dependent upon the degree of extracellular acidification. The maximum level of contraction observed at pH 6.5 was 84.6 +/- 3.4% of the 64.8 mM KCl-induced contraction. To investigate the role of extracellular as well as intracellular Ca(2+) in acidic pH-induced contraction (APIC), we changed the extracellular pH in the presence of EGTA. Sustained contraction induced by acidic pH in the presence of extracellular Ca(2+) was completely abolished in the presence of EGTA, while a transient but significant contraction was still observed. Ryanodine, a selective ryanodine receptor blocker and cyclopiazonic acid (CPA), an inhibitor of sarco-/endoplasmic reticulum Ca(2+) ATPase, abolished the transient contraction, when pH was decreased in Ca(2+)-free solution. On the other hand, neither xestospongin C, a selective inositol-1,4,5-trisphosphate receptor antagonist nor U-73122, a phospholipase C inhibitor showed this effect. These results suggest the involvement of Ca(2+) release from ryanodine-/CPA-sensitive store of sarcoplasmic reticulum (SR). In normal Ca(2+)-containing solution, ryanodine and CPA did not alter the maximum level of APIC. However, they significantly decreased the rate of rise of APIC. U-73122, suppressed the maximum contraction induced by acidic pH without affecting the rate of rise of APIC, while xestospongin C and U-73343, an inactive analogue of U-73122, had no effect on both parameters of APIC. From these results, it is concluded that acidic pH induces Ca(2+) release from the ryanodine-/CPA-sensitive store of SR and that release provides supportive effect on initiating rapid transient contraction, but not on the sustained contraction, which is entirely due to Ca(2+) influx.
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Affiliation(s)
- Dileep Kumar Rohra
- Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aoba-ku, Aramaki, Sendai, 980-8578, Japan
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39
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Smith RD, Eisner DA, Wray S. PH-induced changes in calcium: functional consequences and mechanisms of action in guinea pig portal vein. Am J Physiol Heart Circ Physiol 2002; 283:H2518-26. [PMID: 12427597 DOI: 10.1152/ajpheart.01102.2001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of changing extracellular (pH(o)) and intracellular pH (pH(i)) on force and the mechanisms involved in the guinea pig portal vein were investigated to better understand the control of tone in this vessel. When pH(o) was altered, the effects on force and calcium were the same irrespective of whether force had been produced spontaneously by high-K depolarization or by norepinephrine; alkalinization increased tone, and acidification reduced it. Because pH(o) changes also lead to changes in pH(i), we determined whether the effects on force could be explained by these induced pH(i) changes. It was found, however, that only with spontaneous activity did intracellular alkalinization increase force. In depolarized preparations, force was decreased, and, with norepinephrine, force was initially decreased and then increased. Thus the effects of pH(o) cannot be explained solely by changes in pH(i). The role of the sarcoplasmic reticulum (SR) and surface membrane Ca(2+)-ATPase on the mechanism were investigated and shown not to be involved. Therefore, it is concluded that both pH(o) and pH(i) can have powerful modulatory effects on portal vein tone, that these effects are not identical, and that they are likely to be due to effects of pH on ion channels rather than the SR or plasma membrane Ca(2+)-ATPase.
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Affiliation(s)
- R D Smith
- Department of Physiology, The University of Liverpool, United Kingdom.
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40
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Heppner TJ, Bonev AD, Santana LF, Nelson MT. Alkaline pH shifts Ca2+ sparks to Ca2+ waves in smooth muscle cells of pressurized cerebral arteries. Am J Physiol Heart Circ Physiol 2002; 283:H2169-76. [PMID: 12427589 DOI: 10.1152/ajpheart.00603.2002] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effects of external pH (7.0-8.0) on intracellular Ca(2+) signals (Ca(2+) sparks and Ca(2+) waves) were examined in smooth muscle cells from intact pressurized arteries from rats. Elevating the external pH from 7.4 to 7.5 increased the frequency of local, Ca(2+) transients, or "Ca(2+) sparks," and, at pH 7.6, significantly increased the frequency of Ca(2+) waves. Alkaline pH-induced Ca(2+) waves were inhibited by blocking Ca(2+) release from ryanodine receptors but were not prevented by inhibitors of voltage-dependent Ca(2+) channels, phospholipase C, or inositol 1,4,5-trisphosphate receptors. Activating ryanodine receptors with caffeine (5 mM) at pH 7.4 also induced repetitive Ca(2+) waves. Alkalization from pH 7.4 to pH 7.8-8.0 induced a rapid and large vasoconstriction. Approximately 82% of the alkaline pH-induced vasoconstriction was reversed by inhibitors of voltage-dependent Ca(2+) channels. The remaining constriction was reversed by inhibition of ryanodine receptors. These findings indicate that alkaline pH-induced Ca(2+) waves originate from ryanodine receptors and make a minor, direct contribution to alkaline pH-induced vasoconstriction.
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Affiliation(s)
- Thomas J Heppner
- Department of Pharmacology, University of Vermont College of Medicine, Burlington 05405-0068, USA
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Hattori K, Tsuchida S, Tsukahara H, Mayumi M, Tanaka T, Zhang L, Taniguchi T, Muramatsu I. Augmentation of NO-mediated vasodilation in metabolic acidosis. Life Sci 2002; 71:1439-47. [PMID: 12127164 DOI: 10.1016/s0024-3205(02)01914-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Reduction of perivascular pH in acidemia produces hyporesponsiveness of vascular bed to vasoconstrictors. In the present study, we examined the effects of modest acidification on dilatory responses of isolated rat thoracic aorta. Acetylcholine produced endothelium-dependent relaxation in phenylephrine-precontracted aorta, which was markedly enhanced by acidification of Krebs-Henseleit solution from pH 7.4 to 7.0. A similar augmentation was observed in the relaxing responses to NO donors (SNP, SIN-1, SNAP), 8-Br-cGMP and NS-1619 (a putative K(Ca) channel opener and/or Ca channel inhibitor) in endothelium-denuded, phenylephrine-contracted aorta. However, papaverine-induced relaxation was not affected by the change in pH. At pH 7.4, the relaxing responses to acetylcholine and SNP were partially inhibited by charybdotoxin (K(Ca) channel inhibitor) but not glibenclamide (K(ATP) channel inhibitor), while at pH 7.0 the relaxation induced by either drug was not affected by K(+) channel inhibitors. Relaxation induced by 8-Br-cGMP or NS-1619 was not inhibited by charybdotoxin or glibenclamide. Acidification to pH 7.0 increased the cGMP production in response to acetylcholine in endothelium-intact aorta and to SNP in endothelium-denuded aorta. These results show that modest acidification augments NO-mediated relaxation in rat aorta, probably due to an enhancement of cGMP-dependent but K(+) channel-unrelated relaxation mechanisms.
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Affiliation(s)
- Kaoru Hattori
- Department of Pharmacology, School of Medicine, Fukui Medical University, Matsuoka, Fukui 910-1193, Japan
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Joseph D, Tirmizi O, Zhang XL, Crandall ED, Lubman RL. Polarity of alveolar epithelial cell acid-base permeability. Am J Physiol Lung Cell Mol Physiol 2002; 282:L675-83. [PMID: 11880292 DOI: 10.1152/ajplung.00330.2001] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We investigated acid-base permeability properties of electrically resistive monolayers of alveolar epithelial cells (AEC) grown in primary culture. AEC monolayers were grown on tissue culture-treated polycarbonate filters. Filters were mounted in a partitioned cuvette containing two fluid compartments (apical and basolateral) separated by the adherent monolayer, cells were loaded with the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, and intracellular pH was determined. Monolayers in HCO-free Na(+) buffer (140 mM Na(+), 6 mM HEPES, pH 7.4) maintained a transepithelial pH gradient between the two fluid compartments over 30 min. Replacement of apical fluid by acidic (6.4) or basic (8.0) buffer resulted in minimal changes in intracellular pH. Replacement of basolateral fluid by acidic or basic buffer resulted in transmembrane proton fluxes and intracellular acidification or alkalinization. Intracellular alkalinization was blocked > or =80% by 100 microM dimethylamiloride, an inhibitor of Na(+)/H(+) exchange, whereas acidification was not affected by a series of acid/base transport inhibitors. Additional experiments in which AEC monolayers were grown in the presence of acidic (6.4) or basic (8.0) medium revealed differential effects on bioelectric properties depending on whether extracellular pH was altered in apical or basolateral fluid compartments bathing the cells. Acid exposure reduced (and base exposure increased) short-circuit current from the basolateral side; apical exposure did not affect short-circuit current in either case. We conclude that AEC monolayers are relatively impermeable to transepithelial acid/base fluxes, primarily because of impermeability of intercellular junctions and of the apical, rather than basolateral, cell membrane. The principal basolateral acid exit pathway observed under these experimental conditions is Na(+)/H(+) exchange, whereas proton uptake into cells occurs across the basolateral cell membrane by a different, undetermined mechanism. These results are consistent with the ability of the alveolar epithelium to maintain an apical-to-basolateral (air space-to-blood) pH gradient in situ.
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Affiliation(s)
- Dilip Joseph
- Division of Pulmonary and Critical Care Medicine, Will Rogers Institute Pulmonary Research Center, University of Southern California, Keck School of Medicine, 2011 Zonal Avenue, Los Angeles, CA 90033, USA
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Yamauchi M, Takahashi H, Iwasaki H, Namiki A. Respiratory acidosis prolongs, while alkalosis shortens, the duration and recovery time of vecuronium in humans. J Clin Anesth 2002; 14:98-101. [PMID: 11943520 DOI: 10.1016/s0952-8180(01)00361-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
STUDY OBJECTIVE To determine the effects of respiratory acidosis and alkalosis by mechanical ventilation on the onset, duration, and recovery times of vecuronium. DESIGN Randomized, prospective study. SETTING Operating rooms in the Sapporo Medical University Hospital and Kitami Red Cross Hospital. PATIENTS 90 ASA physical status I and II patients undergoing lower abdominal surgery. INTERVENTIONS Patients were randomly allocated to one of three groups by arterial carbon dioxide tension level (PaCO2; mmHg) after induction: hyperventilation group (PaCO2 = 25-35), normoventilation group (PaCO2 = 35-45), and hypoventilation group (PaCO2 = 45-55). Anesthesia was maintained by spinal block with inhalation of 50% to 66% nitrous oxide in oxygen and intermittent intravenous administration of fentanyl and midazolam with tracheal intubation. MEASUREMENTS AND MAIN RESULTS After vecuronium 0.08 mg/kg was given, onset, duration, and recovery time were measured by mechanomyography (Biometer Myograph 2,000, Odense, Denmark). There were significant differences in the duration and recovery time of vecuronium among the normoventilation group (12.7 +/- 3.3 min and 11.8 +/- 2.8 min, respectively), the hyperventilation group (10.6 +/- 3.5 min and 9.2 +/- 2.7 min, respectively; p < 0.01), and the hypoventilation group (14.4 +/- 3.1 min and 15.0 +/- 3.7 min, respectively; p < 0.01) (mean SD). The closest significant correlation in this study was observed between recovery time and arterial blood pH (r = 0.57; p < 0.05). CONCLUSION In humans, duration and recovery times of vecuronium are prolonged in respiratory acidosis and shortened in respiratory alkalosis.
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Khong TK, McIntyre DJ, Sagnella GA, Markandu ND, Miller MA, Baker EH, Griffiths JR, MacGregor GA. In-vivo intracellular pH at rest and during exercise in patients with essential hypertension. J Hypertens 2001; 19:1595-600. [PMID: 11564979 DOI: 10.1097/00004872-200109000-00011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Several studies in isolated cells have reported that intracellular pH (pHi) in individuals with essential hypertension may be relatively alkaline compared to normotensive individuals. Such an abnormality of pHi in hypertension would be consistent with enhanced sodium-hydrogen exchanger activity and may provide potential mechanisms by which hypertension and its complications could develop. OBJECTIVES To determine in-vivo intracellular pH of skeletal muscle at rest and during recovery from exercise-induced acidosis in hypertensive and normotensive subjects. METHODS Using 31-phosphorus magnetic resonance spectroscopy, pHi of the dominant flexor digitorum superficialis was measured in 20 Caucasian subjects (14 male) with essential hypertension and 20 normotensive controls matched for gender, age, race and body mass index. Measurements were made at rest and during the exercise and recovery periods of a stepped incremental maximal exercise protocol. The rate of pHi recovery from exercise-induced acidosis was calculated by linear regression over the first 210 s of recovery from the pHi time plots of respective subjects. RESULTS Mean resting pHi in the hypertensive (7.05 +/- 0.04) and normotensive groups (7.06 +/- 0.04) were not significantly different. There was a significant effect of gender on pHi: mean pHi was 7.07 +/- 0.03 in males and 7.02 +/- 0.03 in females, respectively (P < 0.0005). The mean intracellular pH achieved by exercise was 6.74 +/- 0.31 in hypertensive individuals and not significantly different in normotensive individuals (6.68 +/- 0.19; P = 0.4). The mean rate of pHi recovery in the hypertensives was 0.08 +/- 0.03 pH units/min and not significantly different in normotensives (0.08 +/- 0.02; P = 0.4). CONCLUSIONS These results contrast with previously documented abnormalities in the control of pHi in hypertension and demonstrate the absence of major in-vivo disturbances of pHi in skeletal muscle, both at rest and during recovery from exercise-induced acidosis, in essential hypertension. Therefore, it is possible that previously documented abnormalities of pHi and activity of the exchanger may be either specific to cell type or not present under in-vivo conditions.
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Affiliation(s)
- T K Khong
- Blood Pressure Unit, St George's Hospital Medical School, London, UK.
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Lindauer U, Kunz A, Schuh-Hofer S, Vogt J, Dreier JP, Dirnagl U. Nitric oxide from perivascular nerves modulates cerebral arterial pH reactivity. Am J Physiol Heart Circ Physiol 2001; 281:H1353-63. [PMID: 11514307 DOI: 10.1152/ajpheart.2001.281.3.h1353] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the isolated rat middle cerebral artery (MCA) we investigated the role of nitric oxide (NO)/cGMP in the vasodilatory response to extraluminal acidosis. Acidosis increased vessel diameter from 140 +/- 27 microm (pH 7.4) to 187 +/- 30 microm (pH 7.0, P < 0.01). NO synthase (NOS) inhibition by N(omega)-nitro-L-arginine (L-NNA, 10 microM) reduced baseline diameter (103 +/- 20 microm, P < 0.01) and attenuated response to acidosis (9 +/- 8 microm). Application of the NO-donors 3-morpholinosydnonimine (1 microM) or S-nitroso-N-acetylpenicillamine (1 microM), or of 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP, 100 microM) reestablished pre-L-NNA diameter at pH 7.4 and reversed L-NNA-induced attenuation of the vessel response to acidosis. Restoration of pre-L-NNA diameter (pH 7.4) by papaverine (20 microM) or nimodipine (30 nM) had no effect on the attenuated response to acidosis. Guanylyl cyclase inhibition with 1H-[1,2,4]oxadiazolo[4,3-a]-quinoxalin-1-one (5 microM) or NOS-inhibition with 7-nitroindazole (7-NI, 100 microM) reduced baseline vessel diameter (109 +/- 8 or 127 +/- 11 microm, respectively) and vasodilation to acidosis, and restoration of baseline diameter with 8-BrcGMP (30 microM) completely restored dilation to pH 7.0. Chronic denervation of NOS-containing perivascular nerves in vivo 14 days before artery isolation significantly reduced pH-dependent reactivity in vitro (diameter increase sham: 48 +/- 14 microm, denervated: 14 +/- 8 microm), and 8-BrcGMP (30 microM) restored dilation to pH 7.0 (denervated: 49 +/- 31 microm). Removal of the endothelium did not change vasodilation to acidosis. We conclude that NO, produced by neuronal NOS of perivascular nerves, is a modulator in the pH-dependent vasoreactivity.
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Affiliation(s)
- U Lindauer
- Department of Experimental Neurology, Humboldt University, Charité Hospital, 10098 Berlin, Germany.
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Akinola AB, Smith GD, Mathias CJ, Land J, Watson L, Puvi-Rajasingham S, Magnifico F. The metabolic, catecholamine and cardiovascular effects of exercise in human sympathetic denervation. Clin Auton Res 2001; 11:251-7. [PMID: 11710798 DOI: 10.1007/bf02298957] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The cardiovascular and metabolic responses to supine leg exercise were measured in 9 healthy subjects (controls) and in 19 subjects with two primary forms of autonomic failure (11 with peripheral sympathetic denervation [pure autonomic failure; PAF], 8 with central sympathetic failure [multiple system atrophy; MSA]). With exercise, blood pressure increased in controls and fell markedly in subjects with PAF and MSA. Blood pressure returned to baseline in controls, but remained low in the PAF and MSA groups. With exercise, heart rate increased more in controls than the PAF and MSA groups. Resting plasma noradrenaline concentrations in controls and in subjects with MSA were similar, but were lower in subjects with PAF. With exercise, plasma noradrenaline concentrations increased in controls and were unchanged in subjects with PAF; there was no significant increase in the MSA group. Resting plasma lactate, pyruvate and lactate/pyruvate ratios were similar in all three groups. With exercise, lactate concentrations increased until 2 minutes post exercise in all groups. Pyruvate concentrations after 9 minutes' exercise were higher in controls than in the PAF group but were similar to the MSA group; thereafter, concentrations increased similarly in all groups. The lactate/pyruvate ratio increased until 2 minutes post exercise in all groups. Resting plasma free fatty acids, and beta-hydroxybutyrate were similar in all groups. Plasma glycerol concentrations in control and MSA subjects were similar; concentrations were lower in PAF subjects. With exercise, plasma free fatty acids and glycerol concentrations remained unchanged in all groups; beta-hydroxybutyrate concentrations decreased less in control subjects than in PAF and MSA subjects. In conclusion, there were similar concentrations of plasma free fatty acids, glycerol and beta-hydroxybutyrate in control, PAF and MSA subjects; this could indicate up-regulation of beta-receptors in AF, or that sympathetic activity plays a smaller role in lipolysis. Plasma lactate and pyruvate concentrations increased similarly in all groups, despite marked differences in BP; this suggested an impairment of production or clearance of lactate in AF. A role for lactate-induced vasodilatation, not compensated for by sympathetic vasoconstriction, remains speculative.
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Affiliation(s)
- A B Akinola
- Autonomic Unit, University Department of Clinical Neurology, University College London, UK
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47
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Tsai KL, Vaughan-Jones RD, Buckler KJ. A dual acid-influx transport system in the carotid body type I cell. Acid influx in carotid body type I cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2000; 475:723-32. [PMID: 10849714 DOI: 10.1007/0-306-46825-5_72] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2023]
Affiliation(s)
- K L Tsai
- University Laboratory of Physiology, Oxford, UK
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Smirnov SV, Knock GA, Belevych AE, Aaronson PI. Mechanism of effect of extracellular pH on L-type Ca(2+) channel currents in human mesenteric arterial cells. Am J Physiol Heart Circ Physiol 2000; 279:H76-85. [PMID: 10899043 DOI: 10.1152/ajpheart.2000.279.1.h76] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Extracellular pH (pH(o)) influences vasoconstriction partly by modulating Ca(2+) influx through voltage-gated Ca(2+) channels in the vasculature. The mechanism of this effect of pH(o) is, however, controversial. Using the whole cell voltage-clamp technique, we examined the influence of pH(o) on L-type Ca(2+) channel currents in isolated human mesenteric arterial myocytes. Acidification to pH 6.2 and alkalinization to 8.2 from 7.2 decreased by approximately 50% and increased by 25-30%, respectively, the peak amplitude of Ca(2+) and Ba(2+) currents (1.5 and 10 mM), with an apparent pK(a) of 6.8. Activation and inactivation of Ca(2+) and Ba(2+) currents were shifted toward positive membrane voltages during acidification and in the opposite direction during alkalinization. The relationship between the current amplitude and shifts in the gating parameters in solutions of different pH(o) conformed closely to that predicted by the Gouy-Chapman model, in which the divalent cation concentration at the outer surface of the membrane varies with the extent to which protons neutralize the membrane surface potential.
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Affiliation(s)
- S V Smirnov
- Division of Pharmacology and Therapeutics, Centre for Cardiovascular Biology and Medicine, King's College London, London SE1 7EH, United Kingdom.
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Halla TR, Madden JA, Gordon JB. Mediators of alkalosis-induced relaxation of piglet pulmonary veins. Am J Physiol Lung Cell Mol Physiol 2000; 278:L968-73. [PMID: 10781427 DOI: 10.1152/ajplung.2000.278.5.l968] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pulmonary venous constriction leads to significant pulmonary hypertension and increased edema formation in several models using newborns. Although alkalosis is widely used in treating neonatal and pediatric pulmonary hypertension, its effects on pulmonary venous tone have not previously been directly measured. This study sought to determine whether alkalosis caused pulmonary venous relaxation and, if so, to identify the mediator(s) involved. Pulmonary venous rings (500-microm external diameter) were isolated from 1-wk-old piglets and precontracted with the thromboxane mimetic U-46619. Responses to hypocapnic alkalosis were then measured under control conditions after inhibition of endothelium-derived modulator activity or K(+) channels. In control rings, alkalosis caused a 34.4 +/- 4.8% decrease in the U-46619-induced contraction. This relaxation was significantly blunted in rings without functional endothelium and in rings treated with nitric oxide synthase or guanylate cyclase inhibitors. However, neither cyclooxygenase inhibition nor voltage-dependent, calcium-dependent, or ATP-dependent K(+)-channel inhibitors altered alkalosis-induced relaxation. These data suggest that alkalosis caused significant dilation of piglet pulmonary veins that was mediated by the nitric oxide-cGMP pathway.
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Affiliation(s)
- T R Halla
- Departments of Pediatrics and Neurology, Medical College of Wisconsin and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53226, USA
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50
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Wilson DA, Woodward B. Acidosis-induced coronary constriction in the rat heart: evidence for the activation of L-type calcium channels. Heart Vessels 2000; 14:59-66. [PMID: 10651181 DOI: 10.1007/bf02481744] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Perfused rat hearts were used to study the effects of acidosis on coronary tone. When pH was decreased, over the range pH 7.4 to pH 6.2, by reducing perfusate bicarbonate levels, under constant flow conditions, there was a transient decrease in coronary perfusion pressure (CPP), followed by a sustained acidosis-dependent increase in CPP, which reversed when pH was returned to pH 7.4. This increase in CPP was seen at perfusion rates of 5, 10, and 20 ml/min(-1). When using constant pressure perfusion acidosis reduced coronary flow. In a HEPES-buffered bicarbonate-free solution, acidosis did not cause a transient fall in CPP but it did produce a sustained increase in CPP. Addition of ammonium chloride (10 mM) reduced CPP, while washout of ammonium chloride increased CPP. The acidosis-induced increase in CPP was not affected by indomethacin, nitro-L-arginine, the nonselective adenosine receptor antagonist, 8-phenyl theophylline, or the thromboxane receptor antagonist, ZD 1542. The acidosis-induced increase in CPP was independent of the myocardial depressant effects of acidosis, but was attenuated by three different L-type calcium channel blockers. These results demonstrate that the coronary circulation of the rat constricts in response to acidosis. Experiments performed with L-type calcium channel blockers, and the calcium channel activator BAY K8644, suggest that constriction occurs via activation of L-type calcium channels. This would not be expected on the basis of electrophysiological studies, which have shown an inhibition of L-type calcium channels by acidosis.
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Affiliation(s)
- D A Wilson
- Department of Pharmacy & Pharmacology, University of Bath, UK
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