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Huetsch JC, Jiang H, Larrain C, Shimoda LA. The Na+/H+ exchanger contributes to increased smooth muscle proliferation and migration in a rat model of pulmonary arterial hypertension. Physiol Rep 2016; 4:4/5/e12729. [PMID: 26997630 PMCID: PMC4823603 DOI: 10.14814/phy2.12729] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Increased muscularity of small pulmonary vessels, involving enhanced proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs), is a key component of the vascular remodeling underlying the development of pulmonary hypertension (PH). Stimuli such as growth factors and hypoxia induce PASMC alkalinization, proliferation, and migration through upregulation of the Na+/H+ exchanger (NHE), inhibition of which prevents the development of hypoxia‐induced vascular remodeling and PH. We wanted to explore whether NHE was also necessary for pathologic PASMC proliferation and migration in a model of pulmonary arterial hypertension (PAH), a severe form of PH not associated with persistent hypoxia. PASMCs were isolated from rats exposed to SU5416‐hypoxia (SuHx) followed by return to normoxia and from vehicle controls. We measured resting intracellular pH (pHi) and NHE activity using the pH‐sensitive fluorescent dye BCECF‐AM. PASMC proliferation and migration were assessed using BrdU incorporation and transwell filters, respectively. NHE activity was increased in SuHx PASMCs, although resting pHi was unchanged. SuHx PASMCs also exhibited increased proliferation and migration relative to controls, which was attenuated in the setting of pharmacologic inhibition of NHE. Our findings suggest that increased NHE activity contributes to pathologic PASMC function in the SuHx model of PAH, although this effect does not appear to be mediated by global changes in pHi homeostasis.
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Affiliation(s)
- John C Huetsch
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Haiyang Jiang
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Carolina Larrain
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
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Undem C, Luke T, Shimoda LA. Contribution of elevated intracellular calcium to pulmonary arterial myocyte alkalinization during chronic hypoxia. Pulm Circ 2016; 6:93-102. [PMID: 27076907 PMCID: PMC4809666 DOI: 10.1086/685053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In the lung, exposure to chronic hypoxia (CH) causes pulmonary hypertension, a debilitating disease. Development of this condition arises from increased muscularity and contraction of pulmonary vessels, associated with increases in pulmonary arterial smooth muscle cell (PASMC) intracellular pH (pHi) and Ca(2+) concentration ([Ca(2+)]i). In this study, we explored the interaction between pHi and [Ca(2+)]i in PASMCs from rats exposed to normoxia or CH (3 weeks, 10% O2). PASMC pHi and [Ca(2+)]i were measured with fluorescent microscopy and the dyes BCECF and Fura-2. Both pHi and [Ca(2+)]i levels were elevated in PASMCs from hypoxic rats. Exposure to KCl increased [Ca(2+)]i and pHi to a similar extent in normoxic and hypoxic PASMCs. Conversely, removal of extracellular Ca(2+) or blockade of Ca(2+) entry with NiCl2 or SKF 96365 decreased [Ca(2+)]i and pHi only in hypoxic cells. Neither increasing pHi with NH4Cl nor decreasing pHi by removal of bicarbonate impacted PASMC [Ca(2+)]i. We also examined the roles of Na(+)/Ca(2+) exchange (NCX) and Na(+)/H(+) exchange (NHE) in mediating the elevated basal [Ca(2+)]i and Ca(2+)-dependent changes in PASMC pHi. Bepridil, dichlorobenzamil, and KB-R7943, which are NCX inhibitors, decreased resting [Ca(2+)]i and pHi only in hypoxic PASMCs and blocked the changes in pHi induced by altering [Ca(2+)]i. Exposure to ethyl isopropyl amiloride, an NHE inhibitor, decreased resting pHi and prevented changes in pHi due to changing [Ca(2+)]i. Our findings indicate that, during CH, the elevation in basal [Ca(2+)]i may contribute to the alkaline shift in pHi in PASMCs, likely via mechanisms involving reverse-mode NCX and NHE.
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Affiliation(s)
- Clark Undem
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Trevor Luke
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
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3
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Carre G, Ouedraogo M, Magaud C, Carreyre H, Becq F, Bois P, Supuran CT, Thibaudeau S, Vandebrouck C, Bescond J. Vasorelaxation induced by dodoneine is mediated by calcium channels blockade and carbonic anhydrase inhibition on vascular smooth muscle cells. JOURNAL OF ETHNOPHARMACOLOGY 2015; 169:8-17. [PMID: 25847623 DOI: 10.1016/j.jep.2015.03.037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 03/05/2015] [Accepted: 03/12/2015] [Indexed: 06/04/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Dodoneine (Ddn) is one of the active compounds identified from Agelanthus dodoneifolius (DC.) Polhill and Wiens, a medicinal plant used in traditional medicine for the treatment of hypertension. This dihydropyranone exerts hypotensive and vasorelaxant effects on rats, and two molecular targets have been characterized: the carbonic anhydrase and the L-type calcium channel in cardiomyocytes with biochemical and electrophysiological techniques, respectively. To further evaluate the involvement of these two molecular targets in vasorelaxation, the effect of Ddn on rat vascular smooth muscle was investigated. MATERIAL AND METHODS The effects of Ddn on L-type calcium current and on resting membrane potential were characterized in A7r5 cell line using the whole-cell patch-clamp configuration. The molecular identities of carbonic anhydrase isozymes in smooth muscle cells were examined with RT-PCR. Vascular response was measured on rat aortic rings in an organ bath apparatus and the effect of Ddn on intracellular pH was determined by flow cytometry using the pH-sensitive fluorescent probe BCECF-AM [2,7-Bis-(2-Carboxyethyl)-5-(and-6)-Carboxyfluorescein, Acetoxymethyl Ester]. RESULTS 100µM Ddn reduced calcium current density of about 30%. In addition, carbonic anhydrase II, III, XIII and XIV were shown to be expressed in rat aorta and inhibited in smooth muscle cells by Ddn. This inhibition resulted in a rise in pHi of about 0.31, leading to KCa channel activation, thereby inducing membrane hyperpolarization and vasorelaxation. The results of vascular reactivity experiments obtained with pharmacological tools acting on the L-type calcium current and carbonic anhydrase suggest that Ddn produces its vasorelaxant effect via the inhibition of these two molecular targets. CONCLUSION This study demonstrates that Ddn induced vasorelaxation by targeting two proteins involved in the modulation of excitation-contraction coupling: L-type calcium channels and carbonic anhydrase.
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Affiliation(s)
- Grégoire Carre
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Maurice Ouedraogo
- Laboratoire de Physiologie Animale, Université de Ouagadougou, 03 BP 7021, Ouagadougou 01, Burkina Faso
| | - Christophe Magaud
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Hélène Carreyre
- Superacid group in "Organic Synthesis" team, Université de Poitiers, CNRS UMR 7285 IC2MP, 4 avenue Michel Brunet, Poitiers 86022 Cedex, France
| | - Frédéric Becq
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Patrick Bois
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Claudiu T Supuran
- Università degli Studi di Firenze, Laboratorio di Chimica Bioinorganica, Rm 188, Via della Lastruccia 3, I-50019 Sesto Fiorentino (Firenze), Italy
| | - Sébastien Thibaudeau
- Superacid group in "Organic Synthesis" team, Université de Poitiers, CNRS UMR 7285 IC2MP, 4 avenue Michel Brunet, Poitiers 86022 Cedex, France
| | - Clarisse Vandebrouck
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France
| | - Jocelyn Bescond
- Signalisation et Transports Ioniques Membranaires, Université de Poitiers, CNRS ERL 7368; 1 rue Georges Bonnet F-86073 Poitiers Cedex 09, France.
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4
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Huetsch J, Shimoda LA. Na(+)/H(+) exchange and hypoxic pulmonary hypertension. Pulm Circ 2015; 5:228-43. [PMID: 26064449 DOI: 10.1086/680213] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 07/22/2014] [Indexed: 12/24/2022] Open
Abstract
Intracellular pH (pHi) homeostasis is key to the functioning of vascular smooth muscle cells, including pulmonary artery smooth muscle cells (PASMCs). Sodium-hydrogen exchange (NHE) is an important contributor to pHi control in PASMCs. In this review, we examine the role of NHE in PASMC function, in both physiologic and pathologic conditions. In particular, we focus on the contribution of NHE to the PASMC response to hypoxia, considering both acute hypoxic pulmonary vasoconstriction and the development of pulmonary vascular remodeling and pulmonary hypertension in response to chronic hypoxia. Hypoxic pulmonary hypertension remains a disease with limited therapeutic options. Thus, this review explores past efforts at disrupting NHE signaling and discusses the therapeutic potential that such efforts may have in the field of pulmonary hypertension.
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Affiliation(s)
- John Huetsch
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA
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Fujii N, Honda Y, Komura K, Tsuji B, Sugihara A, Watanabe K, Kondo N, Nishiyasu T. Effect of voluntary hypocapnic hyperventilation on the relationship between core temperature and heat loss responses in exercising humans. J Appl Physiol (1985) 2014; 117:1317-24. [PMID: 25257867 DOI: 10.1152/japplphysiol.00334.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Two thermolytic thermoregulatory responses, cutaneous vasodilation and sweating, begin when core temperature reaches a critical threshold, after which response magnitudes increase linearly with increasing core temperature; thus the slope indicates response sensitivity. We evaluated the influence of hypocapnia induced by voluntary hyperventilation on the core temperature threshold and sensitivity of thermoregulatory responses. Ten healthy males performed 15 min of cycling at 117 W (29.5°C, 50% RH) under three breathing conditions: 1) spontaneous ventilation, 2) voluntary normocapnic hyperventilation, and 3) voluntary hypocapnic hyperventilation. In the hypocapnic hyperventilation trial, end-tidal CO2 pressure was reduced throughout the exercise, whereas it was maintained around the normocapnic level in the other two trials. Cutaneous vascular conductances at the forearm and forehead were evaluated as laser-Doppler signal/mean arterial blood pressure, and the forearm sweat rate was measured using the ventilated capsule method. Esophageal temperature threshold was higher for the increase in cutaneous vascular conductance in the hypocapnic than normocapnic hyperventilation trial at the forearm (36.88 ± 0.36 vs. 36.68 ± 0.34°C, P < 0.05) and forehead (36.89 ± 0.31 vs. 36.75 ± 0.31°C, P < 0.05). The slope relating esophageal temperature to cutaneous vascular conductance was decreased in the hypocapnic than normocapnic hyperventilation trial at the forearm (302 ± 177 vs. 420 ± 178% baseline/°C, P < 0.05) and forehead (236 ± 164 vs. 358 ± 221% baseline/°C, P < 0.05). Neither the threshold nor the slope for the forearm sweat rate differed significantly between the hypocapnic or normocapnic hyperventilation trials. These findings indicate that in exercising humans, hypocapnia induced by voluntary hyperventilation does not influence sweating, but it attenuates the cutaneous vasodilatory response by increasing its threshold and reducing its sensitivity.
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Affiliation(s)
- Naoto Fujii
- Institute of Health and Sports Sciences, University of Tsukuba, Tsukuba, Japan; and
| | - Yasushi Honda
- Institute of Health and Sports Sciences, University of Tsukuba, Tsukuba, Japan; and
| | - Ken Komura
- Institute of Health and Sports Sciences, University of Tsukuba, Tsukuba, Japan; and
| | - Bun Tsuji
- Institute of Health and Sports Sciences, University of Tsukuba, Tsukuba, Japan; and
| | - Akira Sugihara
- Institute of Health and Sports Sciences, University of Tsukuba, Tsukuba, Japan; and
| | - Kazuhito Watanabe
- Institute of Health and Sports Sciences, University of Tsukuba, Tsukuba, Japan; and
| | - Narihiko Kondo
- Faculty of Human Development, Kobe University, Kobe, Japan
| | - Takeshi Nishiyasu
- Institute of Health and Sports Sciences, University of Tsukuba, Tsukuba, Japan; and
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Pickerodt PA, Francis RC, Höhne C, Neubert F, Telalbasic S, Boemke W, Swenson ER. Pulmonary vasodilation by acetazolamide during hypoxia: impact of methyl-group substitutions and administration route in conscious, spontaneously breathing dogs. J Appl Physiol (1985) 2014; 116:715-23. [PMID: 24481964 DOI: 10.1152/japplphysiol.01235.2013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Acetazolamide (ACZ) prevents hypoxic pulmonary vasoconstriction (HPV) in isolated lungs, animals, and humans, but not by carbonic anhydrase (CA) inhibition. We studied administration routes in, and certain structural aspects of, ACZ critical to HPV inhibition. Analogs of ACZ during acute hypoxia were tested in unanesthetized dogs. Dogs breathed normoxic gas for 1 h (inspired O2 fraction = 0.21), followed by 10% O2 for 2 h (hypoxia) in these protocols: 1) controls; 2) ACZ intravenously (2 mg · kg(-1) · h(-1)); 3) ACZ orally (5 mg/kg, 12 and 1 h before the experiment); 4) inhaled ACZ (750 mg); 5) methazolamide (MTZ) intravenously (3 mg · kg(-1) · h(-1)); and 6) N-methyl-acetazolamide (NMA) intravenously (10 mg · kg(-1) · h(-1)). In controls, mean pulmonary arterial pressure (MPAP) increased 7 mmHg, and pulmonary vascular resistance (PVR) 224 dyn · s · cm(-5) with hypoxia (P < 0.05). With intravenous and inhaled ACZ, MPAP and PVR did not change during hypoxia. With oral ACZ, HPV was only slightly suppressed; MPAP increased 5 mmHg and PVR by 178 dyn · s · cm(-5) during hypoxia. With MTZ and NMA, the MPAP rise (4 ± 2 mmHg) was reduced, and PVR did not increase during hypoxia compared with normoxia (MTZ intravenous: 81 ± 77 and 68 ± 82 dyn · s · cm(-5) with NMA intravenous). Inhaled ACZ prevents HPV, but not without causing systemic CA inhibition. NMA, a compound lacking CA inhibiting effects by methylation at the sulfonamide moiety, and MTZ, a CA-inhibiting analog methylated at the thiadiazole ring, are only slightly less effective than ACZ in reducing HPV.
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Affiliation(s)
- Philipp A Pickerodt
- Department of Anesthesiology and Intensive Care Medicine, Campus Charité Mitte and Campus Virchow-Klinikum, Charité-University Medicine, Berlin, Germany
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7
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Abstract
Carbonic anhydrase (CA) inhibitors, particularly acetazolamide, have been used at high altitude for decades to prevent or reduce acute mountain sickness (AMS), a syndrome of symptomatic intolerance to altitude characterized by headache, nausea, fatigue, anorexia and poor sleep. Principally CA inhibitors act to further augment ventilation over and above that stimulated by the hypoxia of high altitude by virtue of renal and endothelial cell CA inhibition which oppose the hypocapnic alkalosis resulting from the hypoxic ventilatory response (HVR), which acts to limit the full expression of the HVR. The result is even greater arterial oxygenation than that driven by hypoxia alone and greater altitude tolerance. The severity of several additional diseases of high attitude may also be reduced by acetazolamide, including high altitude cerebral edema (HACE), high altitude pulmonary edema (HAPE) and chronic mountain sickness (CMS), both by its CA-inhibiting action as described above, but also by more recently discovered non-CA inhibiting actions, that seem almost unique to this prototypical CA inhibitor and are of most relevance to HAPE. This chapter will relate the history of CA inhibitor use at high altitude, discuss what tissues and organs containing carbonic anhydrase play a role in adaptation and maladaptation to high altitude, explore the role of the enzyme and its inhibition at those sites for the prevention and/or treatment of the four major forms of illness at high altitude.
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Affiliation(s)
- Erik R Swenson
- VA Puget Sound Health Care System and Department of Medicine, University of Washington, Seattle, WA, USA,
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8
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Abstract
It has been known for more than 60 years, and suspected for over 100, that alveolar hypoxia causes pulmonary vasoconstriction by means of mechanisms local to the lung. For the last 20 years, it has been clear that the essential sensor, transduction, and effector mechanisms responsible for hypoxic pulmonary vasoconstriction (HPV) reside in the pulmonary arterial smooth muscle cell. The main focus of this review is the cellular and molecular work performed to clarify these intrinsic mechanisms and to determine how they are facilitated and inhibited by the extrinsic influences of other cells. Because the interaction of intrinsic and extrinsic mechanisms is likely to shape expression of HPV in vivo, we relate results obtained in cells to HPV in more intact preparations, such as intact and isolated lungs and isolated pulmonary vessels. Finally, we evaluate evidence regarding the contribution of HPV to the physiological and pathophysiological processes involved in the transition from fetal to neonatal life, pulmonary gas exchange, high-altitude pulmonary edema, and pulmonary hypertension. Although understanding of HPV has advanced significantly, major areas of ignorance and uncertainty await resolution.
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Affiliation(s)
- J. T. Sylvester
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Larissa A. Shimoda
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Philip I. Aaronson
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
| | - Jeremy P. T. Ward
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland; and Division of Asthma, Allergy and Lung Biology, School of Medicine, King's College, London, United Kingdom
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9
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Ko EA, Song MY, Donthamsetty R, Makino A, Yuan JXJ. Tension Measurement in Isolated Rat and Mouse Pulmonary Artery. ACTA ACUST UNITED AC 2011; 7:123-130. [PMID: 23175638 DOI: 10.1016/j.ddmod.2011.04.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Arterial vasoconstriction is an important physiological process in regulating blood pressure, and is involved in pathologies. The isolation of arteries from rats and mice, as well as the measurement of vascular tension in an ex vivo preparation, are important methods in studying the physiology of arteries and the pathophysiology associated with arterials. Three major methods to measure vascular tension are organ bath, wire myograph, and pressurized arterial myograph. The major method to measure vascular remodeling is by observing the zero-stress state of an artery.
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Affiliation(s)
- Eun A Ko
- Departments of Medicine, University of Illinois at Chicago, Chicago, IL 60612
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10
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Kawaai H, Seino H, Yamazaki S, Taki K. Changes in leukocyte migration during carbonic anhydrase activity inhibition. Burns 2009; 35:397-404. [DOI: 10.1016/j.burns.2008.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2007] [Accepted: 08/21/2008] [Indexed: 12/12/2022]
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Shimoda LA, Luke T, Sylvester JT, Shih HW, Jain A, Swenson ER. Inhibition of hypoxia-induced calcium responses in pulmonary arterial smooth muscle by acetazolamide is independent of carbonic anhydrase inhibition. Am J Physiol Lung Cell Mol Physiol 2007; 292:L1002-12. [PMID: 17209136 DOI: 10.1152/ajplung.00161.2006] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hypoxic pulmonary vasoconstriction (HPV) occurs with ascent to high altitude and can contribute to development of high altitude pulmonary edema (HAPE). Vascular smooth muscle contains carbonic anhydrase (CA), and acetazolamide (AZ), a CA inhibitor, blunts HPV and might be useful in the prevention of HAPE. The mechanism by which AZ impairs HPV is uncertain. Originally developed as a diuretic, AZ also has direct effects on systemic vascular smooth muscle, including modulation of pH and membrane potential; however, the effect of AZ on pulmonary arterial smooth muscle cells (PASMCs) is unknown. Since HPV requires Ca2+ influx into PASMCs and can be modulated by pH, we hypothesized that AZ alters hypoxia-induced changes in PASMC intracellular pH (pH(i)) or Ca2+ concentration ([Ca2+](i)). Using fluorescent microscopy, we tested the effect of AZ as well as two other potent CA inhibitors, benzolamide and ethoxzolamide, which exhibit low and high membrane permeability, respectively, on hypoxia-induced responses in PASMCs. Hypoxia caused a significant increase in [Ca2+](i) but no change in pH(i). All three CA inhibitors slightly decreased basal pH(i), but only AZ caused a concentration-dependent decrease in the [Ca2+](i) response to hypoxia. AZ had no effect on the KCl-induced increase in [Ca2+](i) or membrane potential. N-methyl-AZ, a synthesized compound lacking the unsubstituted sulfonamide group required for CA inhibition, had no effect on pH(i) but inhibited hypoxia-induced Ca2+ responses. These results suggest that AZ attenuates HPV by selectively inhibiting hypoxia-induced Ca2+ responses via a mechanism independent of CA inhibition, changes in pH(i), or membrane potential.
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Affiliation(s)
- Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, MD 21224, USA.
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12
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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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13
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Swenson ER. Carbonic anhydrase inhibitors and hypoxic pulmonary vasoconstriction. Respir Physiol Neurobiol 2005; 151:209-16. [PMID: 16376158 DOI: 10.1016/j.resp.2005.10.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 10/05/2005] [Accepted: 10/05/2005] [Indexed: 11/20/2022]
Abstract
Acetazolamide and other related carbonic anhydrase (CA) inhibitors have had a long history of effectiveness in prevention and treatment of acute mountain sickness (AMS) and remain the standard of care for this indication. Despite many decades of CA inhibitor use for AMS, the possibility has never been seriously entertained that these drugs might also afford protection against high altitude pulmonary edema (HAPE). In this paper, I will present our evidence and supporting data of others, that acetazolamide has inhibitory effects on the hypoxic response of the pulmonary circulation that may be useful in HAPE. Data from pulmonary artery smooth muscle cells, isolated perfused lungs, and live unanethetized animals all point to a potent reduction in hypoxic pulmonary vasoconstriction (HPV) by acetazolamide that may have clinical utility in HAPE and possibly other pulmonary hypertensive disorders. Astonishingly, the efficacy of acetazolamide as a HPV inhibitor does not appear to be related to carbonic anhydrase inhibition, since other potent CA inhibitors have no effect on HPV either in the conscious dog or on hypoxic calcium (Ca(2+)) signalling in rat pulmonary artery smooth muscle cells, despite enzyme presence in these cells. Although we have not yet determined the mechanism of action for acetazolamide in HPV, we have ruled out actions on membrane L-type Ca(2+) channels, normoxic and hypoxic membrane potential and rho-kinase activation. Based upon these negative findings in isolated pulmonary artery smooth muscle cells and preliminary data in Ca(2+) free media we propose that acetazolamide may act at the level of Ca(2+) release from the sarcoplasmic reticulum, a process which initiates and amplifies cell membrane Ca(2+) channel opening. In further work, we have developed and will use a methylated analog of acetazolamide to yield a molecule lacking CA inhibiting activity, but which in most other respects (size, pK(a), heterocyclic ring structure, electrostatic charge distribution) is equivalent to acetazolamide.
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Affiliation(s)
- Erik R Swenson
- Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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14
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Eichler W, Bechtel MJF, Klaus S, Heringlake M, Hernandez M, Toerber K, Klotz KF, Bartels C. Na /H+ exchange inhibitor cariporide: effects on respiratory dysfunction after cardiopulmonary bypass. Perfusion 2004; 19:33-40. [PMID: 15072253 DOI: 10.1191/0267659104pf712oa] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The purpose of the present study was to evaluate the potential of the Na+/H+ exchange inhibitor cariporide to protect the lung from injury after cardiopulmonary bypass (CPB). In a randomized placebo-controlled study, 16 pigs were subjected to CPB for 75 min. Administration of vehicle or cariporide (bolus 180 mg, 40 mg/hour) began 30 min pre-CPB and was continued throughout the protocol. The alveolo-arterial O2-gradient (AaDO2), the pulmonary shunt (Qs/Qt), the compliance (Cpl), haemodynamic variables and glycerol and water content in lung tissue were measured 10 min before and up to 180 min post-CPB. All animals in the control versus 75% in the cariporide group survived the experiment. At 5 and 60 min post-CPB, the mean AaDO2 and at 5, 60 and 180 min post-CPB, the mean pulmonary vascular resistance index were higher in the cariporide group (p < 0.05), respectively. More lung water accumulation was found in the cariporide group (p < 0.05). Mean Cpl decreased; the Qs/ Qt and glycerol in lung tissue increased without significant intergroup difference. In this model, the inhibitor of the Na+/H+ antiporter showed no protective effect on lung injury after CPB and might even have harmful effects on pulmonary vascular tone and function.
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15
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Mustafa S, Thulesius O. Cooling-induced carotid artery dilatation: an experimental study in isolated vessels. Stroke 2002; 33:256-60. [PMID: 11779919 DOI: 10.1161/hs0102.101545] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Clinical and experimental studies seem to indicate that hypothermia may improve outcome in stroke victims and reduce experimental brain injury. The current interpretation is that cooling has a neuroprotective effect by reducing brain metabolism. The objective of our study was to test the hypothesis that hypothermia induces arterial vasodilatation and thereby increases cerebral blood flow. METHODS We recorded isometric tension in rabbit carotid artery strips in organ baths during stepwise cooling. The cooling responses were tested at basal tone, in noradrenaline-precontracted vessels, and after electric field stimulation. RESULTS Stepwise cooling from 37 degrees C to 4 degrees C induced reproducible graded relaxation, inversely proportional to temperature. The responses could be elicited at basal tone and in precontracted vessels. Cooling decreased the contractile responses to norepinephrine and potassium chloride. Cooling at 20 degrees C decreased the contractile responses to electric field stimulation, while at 10 degrees C these were totally abolished. Cooling-induced vasodilatation is not dependent on an endothelial mechanism. CONCLUSIONS Cooling of carotid artery preparations induced a reversible graded vasodilatation and decreased or abolished the effect of vasocontractile neurotransmitters. The effect of local hypothermia could increase cerebral blood flow and may constitute a positive therapeutic modality in stroke patients.
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Affiliation(s)
- Seham Mustafa
- Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait.
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16
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Mustafa SMD, Thulesius O. Cooling is a potent vasodilator of deep vessels in the rat. Can J Physiol Pharmacol 2001. [DOI: 10.1139/y01-073] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The objectives of this study were to determine the effect of cooling on smooth muscle tone of the pulmonary artery and aorta and to clarify the basic mechanism of these responses. We recorded isometric tension in smooth muscle strips of rat pulmonary artery and aorta in organ baths during stepwise cooling. Cooling responses were tested before and after the addition of various standard agents that interfere with known neurogenic (autonomic blockers, tetrodotoxin) and myogenic mechanisms (calcium channel blockers) of relaxation. We also examined the hypothesis of the presence of a cooling-released substance. Stepwise cooling (37°C to 4°C) of aortic smooth muscle induced reproducible graded relaxations that were inversely proportional to temperature. Cooling-induced relaxation was not dependent on a neural mechanism nor the release of neurotransmitters or a cooling-released substance such as NO or CO. Cooling of pulmonary arterial and aortic smooth muscle preparations induced a graded myogenic relaxation inversely proportional to the cooling temperature. The mechanism is not dependent on local nervous or known mediators but related to a direct physico-chemical effect of cooling.Key words: cooling, vasodilatation, pulmonary artery, aorta.
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17
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Wakabayashi I, Masui H, Groschner K. Intracellular alkalinization augments alpha(1)-adrenoceptor-mediated vasoconstriction by promotion of Ca(2+) entry through the non-L-type Ca(2+) channels. Eur J Pharmacol 2001; 428:251-9. [PMID: 11675043 DOI: 10.1016/s0014-2999(01)01293-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Modulation by intracellular pH of the vasoconstriction induced by alpha-adrenoceptor agonists was investigated in isolated guinea pig aorta. NH(4)Cl (15 mM) increased intracellular pH of aortic smooth muscle cells by about 0.2 pH unit and significantly augmented KCl-induced contraction of aortic strips, whereas simultaneous administration of NH(4)Cl (15 mM) plus Na(+) propionate (30 mM) failed to affect intracellular pH or contractility. NH(4)Cl (15 mM) potentiated contractions induced by alpha-adrenoceptor agonists, norepinephrine, phenylephrine and clonidine. Contraction induced by alpha(1)-selective adrenoceptor agonist, phenylephrine, but not that induced by norepinephrine or clonidine, was insensitive to inhibition by verapamil (1 microM). Phenylephrine-induced contraction was not affected by NH(4)Cl in Ca(2+)-free medium whereas extracellular Ca(2+)-induced contraction of phenylephrine-stimulated aorta was significantly augmented by NH(4)Cl. Consistently, 45Ca(2+)uptake into phenylephrine 1 microM)-stimulated aortic strips was increased by incubation with NH(4)Cl. The potentiating effects of NH(4)Cl on both phenylephrine-induced Ca(2+) entry and contraction were antagonized by Na(+) propionate. These results suggest that intracellular alkalinization facilitates alpha(1)-adrenoceptor-mediated vasoconstriction by facilitation of an agonist-induced Ca(2+) entry pathway that is independent of L-type Ca(2+) channels.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Ammonium Chloride/pharmacology
- Animals
- Aorta/drug effects
- Aorta/physiology
- Calcium/metabolism
- Calcium/pharmacology
- Calcium Channel Blockers/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/physiology
- Clonidine/pharmacology
- Dose-Response Relationship, Drug
- Drug Synergism
- Guinea Pigs
- Hydrogen-Ion Concentration
- In Vitro Techniques
- Male
- Muscle Contraction/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Norepinephrine/pharmacology
- Phenylephrine/pharmacology
- Phorbol 12,13-Dibutyrate/pharmacology
- Potassium Chloride/pharmacology
- Propionates/pharmacology
- Receptors, Adrenergic, alpha-1/drug effects
- Receptors, Adrenergic, alpha-1/physiology
- Vasoconstriction/drug effects
- Vasoconstriction/physiology
- Verapamil/pharmacology
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Affiliation(s)
- I Wakabayashi
- Department of Hygiene and Preventive Medicine, School of Medicine, Yamagata University, Iida-Nishi 2-2-2, Yamagata 990-9585, Japan.
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18
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Vander Heyden MA, Halla TR, Madden JA, Gordon JB. Multiple Ca(2+)-dependent modulators mediate alkalosis-induced vasodilation in newborn piglet lungs. Am J Physiol Lung Cell Mol Physiol 2001; 280:L519-26. [PMID: 11159036 DOI: 10.1152/ajplung.2001.280.3.l519] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We previously found that alkalosis-induced vasodilation was mediated by endothelium-derived nitric oxide (EDNO) in newborn piglet pulmonary artery and vein rings precontracted with the thromboxane mimetic U-46619. In contrast, prostacyclin or K(+) channel activation contributed to the response in other preparations. This study was undertaken to determine whether EDNO alone also mediates alkalosis-induced pulmonary vasodilation in piglet lungs vasoconstricted with hypoxia and, if not, to identify the mediator(s) involved. Responses to alkalosis were measured during hypoxia under control conditions after blocking nitric oxide synthase (N(omega)-nitro-L-arginine), cyclooxygenase (meclofenamate), or both endothelium-derived modulators (Dual); after blocking voltage-dependent (4-aminopyridine), ATP- dependent (glibenclamide), or Ca(2+)-dependent K(+) (K(Ca); tetraethylammonium) K(+) channels; and after blocking both endothelium-derived modulators and K(Ca) channels (Triple). Vasodilator responses measured after 20 min of alkalosis were blunted in Dual and tetraethylammonium lungs and abolished in Triple lungs. Thus alkalosis-induced vasodilation in hypoxic lungs appeared to be mediated by three Ca(2+)-dependent modulators: EDNO, prostacyclin, and K(Ca) channels. In addition, a transient, unidentified modulator contributed to the nadir of the vasodilator response measured at 10 min of alkalosis. Future studies are needed to identify factors that contribute to the discordance between isolated vessels and whole lungs.
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Affiliation(s)
- M A Vander Heyden
- Department of Pediatrics, Medical College of Wisconsin and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53226, USA
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19
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Madden JA, Ray DE, Keller PA, Kleinman JG. Ion exchange activity in pulmonary artery smooth muscle cells: the response to hypoxia. Am J Physiol Lung Cell Mol Physiol 2001; 280:L264-71. [PMID: 11159005 DOI: 10.1152/ajplung.2001.280.2.l264] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purposes of this study were to determine 1) the presence of the major ion transport activities that regulate cytoplasmic pH (pH(c)) in cat pulmonary artery smooth muscle cells, i.e., Na+/H+ and the Na+-dependent and -independent Cl-/HCO3- exchange, 2) whether pH(c) changes in cells from small (SPAs) and large (LPAs) pulmonary arteries during hypoxia, and 3) whether changes in pH(c) are due to changes in the balance of exchange activities. Exchange activities as defined by physiological maneuvers rather than molecular identity were ascertained with fluorescence microscopy to document changes in the ratio of the pH(c) indicator 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein. Steady-state pH(c) was higher in LPA than in SPA normoxic smooth muscle cells. SPAs and LPAs possessed all three transport activities; in HCO3- containing normoxic solutions, Cl-/HCO3- exchange rather than Na+/H+ exchange set the level of pH(c); in HCO3- containing hypoxic solutions, pH(c) increased in SPA and decreased in LPA cells; altering the baseline pH(c) of a cell type to that of the other did not change the direction of the pH(c) response during hypoxia. The absence of Na+ prevented hypoxia-induced alkalinization in SPA cells; in both cell types, inhibiting the Cl-/HCO3- exchange activities reversed the normal direction of pH(c) changes during hypoxia.
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Affiliation(s)
- J A Madden
- Department of Neurology, The Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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20
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Balasubramanyan N, Halla TR, Ghanayem NS, Gordon JB. Endothelium-independent and -dependent vasodilation in alkalotic and acidotic piglet lungs. Pediatr Pulmonol 2000; 30:241-8. [PMID: 10973042 DOI: 10.1002/1099-0496(200009)30:3<241::aid-ppul8>3.0.co;2-k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Although significant pulmonary hypertension can occur in patients treated with either hypocapnic alkalosis or "permissive" hypercapnic acidosis, the effects of sustained alkalosis or acidosis on subsequent vasodilator responses have not been established. This study measured the effects of 60-100 min of sustained alkalosis or acidosis on endothelium-independent and -dependent vasodilation with inhaled nitric oxide (iNO) and acetylcholine (ACh) in isolated lungs from 1-week-old piglets. After stabilization, lungs were divided into control (pH 7.40, PaCO(2) 40 torr, n = 5), alkalotic (pH 7.60, PaCO(2) 25 torr, n = 6), or acidotic (pH 7.25, PaCO(2) 65 torr, n = 5) groups and ventilated with 21% O(2) for 40 min. Acute hypoxic pulmonary vasoconstriction (HPV) was then induced with 4-6% O(2). After a stable pressor response had occurred (approximately 20 min), pulmonary artery dose-response relationships to increasing concentrations of iNO were measured. The iNO was then stopped and after a stable hypoxic pressure had again been reestablished (approximately 20 min), dose-responses to increasing concentrations of ACh were measured. Hypoxic pulmonary vascular resistance (PVR) was similar in all groups. Pulmonary artery pressure dose-response relationships to iNO and ACh were blunted in the alkalosis group, suggesting that both endothelium-independent and -dependent vasodilation were reduced during sustained hypocapnic alkalosis. In contrast, sustained acidosis did not alter subsequent vasodilator responses. Future studies must elucidate the mechanisms underlying blunted pulmonary vasodilation during sustained alkalosis and examine the consequences of sustained alkalosis therapy on subsequent vasodilator responses in clinical practice.
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Affiliation(s)
- N Balasubramanyan
- Department of Pediatrics, Critical Care Section, Medical College of Wisconsin and Veterans Administration Medical Center, Milwaukee, Wisconsin
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21
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Leach RM, Sheehan DW, Chacko VP, Sylvester JT. Energy state, pH, and vasomotor tone during hypoxia in precontracted pulmonary and femoral arteries. Am J Physiol Lung Cell Mol Physiol 2000; 278:L294-304. [PMID: 10666113 DOI: 10.1152/ajplung.2000.278.2.l294] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To assess effects of smooth muscle energy state and intracellular pH (pH(i)) on pulmonary arterial tone during hypoxia, we measured ATP, phosphocreatine, P(i), and pH(i) by (31)P-NMR spectroscopy and isometric tension in phenylephrine-contracted rings of porcine proximal intrapulmonary arteries. Hypoxia caused early transient contraction followed by relaxation and late sustained contraction. Energy state and pH(i) decreased during relaxation and recovered toward control values during late contraction. Femoral arterial rings had higher energy state and lower pH(i) under baseline conditions and did not exhibit late contraction or recovery of energy state and pH(i) during hypoxia. In pulmonary arteries, glucose-free conditions abolished late hypoxic contraction and recovery of energy state and pH(i), but endothelial denudation abolished only late hypoxic contraction. NaCN had little effect at 0. 1 and 1.0 mM but caused marked vasorelaxation and decreases in energy state and pH(i) at 10 mM. These results suggest that 1) regulation of tone, energy state, and pH(i) differed markedly in pulmonary and femoral arterial smooth muscle, 2) hypoxic relaxation was mediated by decreased energy state or pH(i) due to hypoxic inhibition of oxidative phosphorylation, 3) recovery of energy state and pH(i) in hypoxic pulmonary arteries was due to accelerated glycolysis mediated by mechanisms intrinsic to smooth muscle, and 4) late hypoxic contraction in pulmonary arteries was mediated by endothelial factors that required hypoxic recovery of energy state and pH(i) for transduction in smooth muscle or extracellular glucose for production and release by endothelium.
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Affiliation(s)
- R M Leach
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21224, USA
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22
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Gordon JB, Rehorst-Paea LA, Hoffman GM, Nelin LD. Pulmonary vascular responses during acute and sustained respiratory alkalosis or acidosis in intact newborn piglets. Pediatr Res 1999; 46:735-41. [PMID: 10590032 DOI: 10.1203/00006450-199912000-00013] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Acute alkalosis-induced pulmonary vasodilation and acidosis-induced pulmonary vasoconstriction have been well described, but responses were generally measured within 5-30 min of changing pH. In contrast, several in vitro studies have found that relatively brief periods of sustained alkalosis can enhance, and sustained acidosis can decrease, vascular reactivity. In this study of intact newborn piglets, effects of acute (20 min) and sustained (60-80 min) alkalosis or acidosis on baseline (35% O2) and hypoxic (12% O2) pulmonary vascular resistance (PVR) were compared with control piglets exposed only to eucapnia. Acute alkalosis decreased hypoxic PVR, but sustained alkalosis failed to attenuate either baseline PVR or the subsequent hypoxic response. Acute acidosis did not significantly increase hypoxic PVR, but sustained acidosis markedly increased both baseline PVR and the subsequent hypoxic response. Baseline PVR was similar in all piglets after resumption of eucapnic ventilation, but the final hypoxic response was greater in piglets previously exposed to alkalosis than in controls. Thus, hypoxic pulmonary vasoconstriction was not attenuated during sustained alkalosis, but was accentuated during sustained acidosis and after the resumption of eucapnia in alkalosis-treated piglets. Although extrapolation of data from normal piglets to infants and children with pulmonary hypertension must be done with caution, this study suggests that sustained alkalosis may be of limited efficacy in treating acute hypoxia-induced pulmonary hypertension and the risks of pulmonary hypertension must be considered when using ventilator strategies resulting in permissive hypercapnic acidosis.
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Affiliation(s)
- J B Gordon
- Department of Pediatrics , Medical College of Wisconsin, and Zablocki VAMC, Milwaukee, USA
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23
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Moreira GA, O'Donnell DC, Tod ML, Madden JA, Gordon JB. Discordant effects of alkalosis on elevated pulmonary vascular resistance and vascular reactivity in lamb lungs. Crit Care Med 1999; 27:1838-42. [PMID: 10507607 DOI: 10.1097/00003246-199909000-00022] [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: 11/25/2022]
Abstract
OBJECTIVES After an initial vasodilator response to alkalosis, many children with pulmonary hypertension exhibit marked pulmonary vascular reactivity despite continued alkalosis therapy. This study sought to a) identify the mediator of alkalosis-induced pulmonary vasodilation in isolated lamb lungs; b) determine whether alkalosis-induced pulmonary vasodilation decreases over time in this model; and c) determine whether alkalosis enhanced vascular reactivity to subsequent pressor stimuli. DESIGN Prospective, interventional study. SUBJECTS Isolated perfused lungs from 1-month-old lambs. INTERVENTIONS Hypocarbic alkalosis, hypoxia, and infusion of the thromboxane mimetic agent U46619 MEASUREMENTS AND MAIN RESULTS Pulmonary artery pressure was measured at constant flow, so a change in pressure reflects change in resistance. Hypoxic pulmonary artery pressure was compared after 20 and 100 mins of hypocarbic alkalosis or normocarbia in control and cyclooxygenase-inhibited lungs. Pulmonary artery dose responses to U46619 were then measured in control lungs. Responses to hypoxia and U46619 were also compared after 60-80 mins of hypocarbic or normocarbic normoxia. Hypocarbic alkalosis acutely reduced hypoxic pulmonary vascular resistance, and this was sustained for at least 100 mins. Cyclooxygenase inhibition blocked this vasodilation, suggesting that it was mediated by dilator prostaglandins. However, subsequent reactivity to U46619 was enhanced in hypoxic alkalotic lungs, and both hypoxia and U46619 caused significant vasoconstriction in normoxic alkalotic lungs. CONCLUSIONS Alkalosis caused sustained vasodilation when pulmonary vascular resistance was high but either failed to attenuate or enhanced vascular reactivity to subsequent pressor stimuli.
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Affiliation(s)
- G A Moreira
- Department of Pediatrics, University of Maryland School of Medicine, Baltimore, USA
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Leach RM, Sheehan DW, Chacko VP, Sylvester JT. Effects of hypoxia on energy state and pH in resting pulmonary and femoral arterial smooth muscles. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:L1051-60. [PMID: 9843841 DOI: 10.1152/ajplung.1998.275.6.l1051] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To determine the effects of hypoxia on energy state and intracellular pH (pHi) in resting pulmonary and systemic arterial smooth muscles, we used 31P nuclear magnetic resonance spectroscopy and colorimetric and enzymatic assays to measure pHi; intracellular concentrations of ATP, phosphocreatine, creatine, and Pi; and phosphorylation potential in superfused tissue segments from porcine proximal intrapulmonary and superficial femoral arteries. Under baseline conditions (PO2 467 +/- 12.1 mmHg), energy state and total creatine (phosphocreatine + creatine) concentration were lower and pHi was higher in pulmonary arteries. During hypoxia (PO2 23 +/- 2.4 mmHg), energy state deteriorated more in femoral arteries than in pulmonary arteries. pHi fell in both tissues but was always more alkaline in pulmonary arteries. Reoxygenation reversed the changes induced by hypoxia. These results suggest that production and/or elimination of ATP and H+ was different in resting pulmonary and systemic arterial smooth muscles under baseline and hypoxic conditions. Because energy state and pHi affect a wide variety of cellular processes, including signal transduction, contractile protein interaction, and activities of ion pumps and channels, further investigation is indicated to determine whether these differences have functional significance.
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Affiliation(s)
- R M Leach
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21224, USA
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Farrukh IS, Peng W, Orlinska U, Hoidal JR. Effect of dehydroepiandrosterone on hypoxic pulmonary vasoconstriction: a Ca(2+)-activated K(+)-channel opener. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:L186-95. [PMID: 9486202 DOI: 10.1152/ajplung.1998.274.2.l186] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In the present study, we investigated the effects of the naturally occurring hormone dehydroepiandrosterone (DHEA) on hypoxic pulmonary vasoconstriction (HPVC) in isolated ferret lungs and on K+ currents in isolated and cultured ferret pulmonary arterial smooth muscle cells (FPSMCs). Severe alveolar hypoxia (3% O2-5% CO2-92% N2) caused an initial increase in pulmonary arterial pressure (Ppa) that was followed by a reversal in pulmonary hypertension. Maintaining alveolar hypoxia caused a sustained secondary increase in Ppa. Pretreating the lungs with the K(+)-channel inhibitor tetraethylammonium (TEA) caused a small increase in baseline Ppa, potentiated HPVC, and prevented the reversal of HPVC during the sustained alveolar hypoxia. Treating the lungs with DHEA caused a near-complete reversal of HPVC in control lungs and in lungs that were pretreated with TEA. DHEA also reversed the KCl-induced increase in Ppa. In FPSMCs, DHEA caused an adenosine 3',5'-cyclic monophosphate- and guanosine 3',5'-cyclic monophosphate-independent increase in activity of the Ca(2+)-activated K+ (KCa) current. In a cell-attached configuration, DHEA caused a mean shift of -22 mV in the voltage-dependent activation of the KCa channel. We conclude that DHEA is a novel KCa-channel opener of the pulmonary vasculature.
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Affiliation(s)
- I S Farrukh
- Department of Internal Medicine, University of Utah Health Science Center, Salt Lake City 84132, USA
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