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Abstract
Endothelial dysfunction (ED) plays a substantial role in the pathogenesis of atherosclerosis and some other vascular diseases. ED has been demonstrated in patients with hypercholesterolemia, diabetes, smoking, hypertension, and in patients with atherosclerotic disease. Besides classical risk factors, ED is affected by chronic inflammatory diseases and acute infections, particularly viral diseases. Causes of ED include oxidative stress, inflammation, and shear stress, which decrease the bioavailability of nitric oxide. Markers of ED have been sought, particularly circulating markers. Using these tests, it is possible to evaluate the response to harmful effects of risk factors and the effects of treatment on vessel wall function. Endothelial dysfunction is significantly and directly correlated with the occurrence of cardiac events and the risk of cardiac events increase as ED worsens. Because endothelial function plays a central role in atherogenesis it became a therapeutic target. Endothelial dysfunction is reversible and its improvement may be achieved by elimination of risk factors, inhibitors of endothelium-derived contracting factors (angiotensin-converting enzyme), smoking cessation, lipid-lowering drugs, diet, and physical exercise. By reversing ED, it is possible to restore vascular function.
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Affiliation(s)
- Pavel Poredos
- Department of Vascular Disease, 37663University Medical Centre Ljubljana, Slovenia.,Department of Advanced Cardiopulmonary Therapies and Transplantation, 7067The University of Texas Health Science Centre at Houston, TX, USA
| | | | - Igor Gregoric
- Department of Advanced Cardiopulmonary Therapies and Transplantation, 7067The University of Texas Health Science Centre at Houston, TX, USA
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2
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Chu PL, Gigliotti JC, Cechova S, Bodonyi-Kovacs G, Chan F, Ralph DL, Howell N, Kalantari K, Klibanov AL, Carey RM, McDonough AA, Le TH. Renal Collectrin Protects against Salt-Sensitive Hypertension and Is Downregulated by Angiotensin II. J Am Soc Nephrol 2017; 28:1826-1837. [PMID: 28062568 DOI: 10.1681/asn.2016060675] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 11/28/2016] [Indexed: 12/13/2022] Open
Abstract
Collectrin, encoded by the Tmem27 gene, is a transmembrane glycoprotein with approximately 50% homology with angiotensin converting enzyme 2, but without a catalytic domain. Collectrin is most abundantly expressed in the kidney proximal tubule and collecting duct epithelia, where it has an important role in amino acid transport. Collectrin is also expressed in endothelial cells throughout the vasculature, where it regulates L-arginine uptake. We previously reported that global deletion of collectrin leads to endothelial dysfunction, augmented salt sensitivity, and hypertension. Here, we performed kidney crosstransplants between wild-type (WT) and collectrin knockout (Tmem27Y/- ) mice to delineate the specific contribution of renal versus extrarenal collectrin on BP regulation and salt sensitivity. On a high-salt diet, WT mice with Tmem27Y/- kidneys had the highest systolic BP and were the only group to exhibit glomerular mesangial hypercellularity. Additional studies showed that, on a high-salt diet, Tmem27Y/- mice had lower renal blood flow, higher abundance of renal sodium-hydrogen antiporter 3, and lower lithium clearance than WT mice. In WT mice, administration of angiotensin II for 2 weeks downregulated collectrin expression in a type 1 angiotensin II receptor-dependent manner. This downregulation coincided with the onset of hypertension, such that WT and Tmem27Y/- mice had similar levels of hypertension after 2 weeks of angiotensin II administration. Altogether, these data suggest that salt sensitivity is determined by intrarenal collectrin, and increasing the abundance or activity of collectrin may have therapeutic benefits in the treatment of hypertension and salt sensitivity.
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Affiliation(s)
| | - Joseph C Gigliotti
- Division of Nephrology.,Department of Integrated Physiology and Pharmacology, Liberty University College of Osteopathic Medicine, Lynchburg, Virginia; and
| | | | | | | | - Donna Lee Ralph
- Department of Cell and Neurobiology, University of Southern California, Keck School of Medicine, Los Angeles, California
| | - Nancy Howell
- Division of Endocrinology, Department of Medicine, University of Virginia Health System, Charlottesville, Virginia
| | | | | | - Robert M Carey
- Division of Endocrinology, Department of Medicine, University of Virginia Health System, Charlottesville, Virginia
| | - Alicia A McDonough
- Department of Cell and Neurobiology, University of Southern California, Keck School of Medicine, Los Angeles, California
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Moss NG, Gentle TK, Arendshorst WJ. Modulation of the myogenic mechanism: concordant effects of NO synthesis inhibition and O2- dismutation on renal autoregulation in the time and frequency domains. Am J Physiol Renal Physiol 2016; 310:F832-45. [PMID: 26823282 DOI: 10.1152/ajprenal.00461.2015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 01/21/2016] [Indexed: 12/17/2022] Open
Abstract
Renal blood flow autoregulation was investigated in anesthetized C57Bl6 mice using time- and frequency-domain analyses. Autoregulation was reestablished by 15 s in two stages after a 25-mmHg step increase in renal perfusion pressure (RPP). The renal vascular resistance (RVR) response did not include a contribution from the macula densa tubuloglomerular feedback mechanism. Inhibition of nitric oxide (NO) synthase [N(G)-nitro-l-arginine methyl ester (l-NAME)] reduced the time for complete autoregulation to 2 s and induced 0.25-Hz oscillations in RVR. Quenching of superoxide (SOD mimetic tempol) during l-NAME normalized the speed and strength of stage 1 of the RVR increase and abolished oscillations. The slope of stage 2 was unaffected by l-NAME or tempol. These effects of l-NAME and tempol were evaluated in the frequency domain during random fluctuations in RPP. NO synthase inhibition amplified the resonance peak in admittance gain at 0.25 Hz and markedly increased the gain slope at the upper myogenic frequency range (0.06-0.25 Hz, identified as stage 1), with reversal by tempol. The slope of admittance gain in the lower half of the myogenic frequency range (equated with stage 2) was not affected by l-NAME or tempol. Our data show that the myogenic mechanism alone can achieve complete renal blood flow autoregulation in the mouse kidney following a step increase in RPP. They suggest also that the principal inhibitory action of NO is quenching of superoxide, which otherwise potentiates dynamic components of the myogenic constriction in vivo. This primarily involves the first stage of a two-stage myogenic response.
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Affiliation(s)
- Nicholas G Moss
- Department of Cell Biology and Physiology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - Tayler K Gentle
- Department of Cell Biology and Physiology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
| | - William J Arendshorst
- Department of Cell Biology and Physiology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina
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Liu LH, Fan X, Xia ZK, An XX, Yang RY. Angiotensin II stimulates melanogenesis via the protein kinase C pathway. Exp Ther Med 2015; 10:1528-1532. [PMID: 26622519 DOI: 10.3892/etm.2015.2682] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Accepted: 06/16/2015] [Indexed: 11/06/2022] Open
Abstract
Melanogenesis is a physiological process that results in the synthesis of melanin pigments, which serve a crucial function in hyperpigmentation. The aim of the present study was to determine the effects of angiotensin II (Ang II) on melanogenesis and to elucidate the molecular events of Ang II-induced melanogenesis. Experiments were performed on human melanocytes to elucidate the pigmenting effect of Ang II and the underlying mechanisms. The elements involved in melanogenesis, including melanin content, tyrosinase (TYR) activity, and microphthalmia-associated transcription factor (MITF) and TYR expression at the mRNA and protein levels were evaluated. Melanin content and TYR activity increased in response to Ang II treatment in a concentration-dependent manner. MITF and TYR mRNA and protein expression levels were increased significantly in response to Ang II in a concentration-dependent manner. The Ang II-induced increase in melanin synthesis was reduced significantly in response to co-treatment with Ro-32-0432, a protein kinase C (PKC) inhibitor, whereas co-treatment with H-89, a PKA inhibitor, did not attenuate the Ang II-induced increase in melanin levels. These results suggest that PKC is required for Ang II-induced pigmentation in human melanocytes and that the mechanism involves the PKC pathway and MITF upregulation.
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Affiliation(s)
- Li-Hong Liu
- Graduate School, The Third Military Medical University, Chongqing 400038, P.R. China ; Department of Dermatology, General Hospital of Beijing Military Region of PLA, Beijing 100125, P.R. China
| | - Xin Fan
- Department of Dermatology, General Hospital of Beijing Military Region of PLA, Beijing 100125, P.R. China
| | - Zhi-Kuan Xia
- Department of Dermatology, General Hospital of Beijing Military Region of PLA, Beijing 100125, P.R. China
| | - Xu-Xi An
- Department of Dermatology, General Hospital of Beijing Military Region of PLA, Beijing 100125, P.R. China
| | - Rong-Ya Yang
- Department of Dermatology, General Hospital of Beijing Military Region of PLA, Beijing 100125, P.R. China
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Savard S, Lavoie P, Villeneuve C, Agharazii M, Lebel M, Larivière R. eNOS gene delivery prevents hypertension and reduces renal failure and injury in rats with reduced renal mass. Nephrol Dial Transplant 2011; 27:2182-90. [PMID: 22121231 DOI: 10.1093/ndt/gfr641] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Impaired nitric oxide (NO) release in chronic renal failure has been implicated in the pathogenesis of hypertension and the progression of renal insufficiency. We investigated whether gene delivery of the endothelial NO synthase (eNOS) improves NO release and reduces blood pressure and renal failure and injury in rats with reduced renal mass. METHODS Renal failure was induced by renal artery branches ligation. Two weeks later, rats with renal failure were divided into three groups and received an intravenous injection of the vehicle or the adenovirus that expresses eNOS or β-galactosidase (β-gal). Systolic blood pressure, renal parameters and histopathology were assessed at Week 4 after gene delivery. RESULTS At the end of the study, systolic blood pressures, serum creatinine, proteinuria, urinary endothelin-1 (ET-1) excretion and renal cortex ET-1 levels were increased, whereas plasma and urine NO(2)/NO(3) were reduced in renal failure rats as compared to normal controls. Renal injury comprised blood vessel media hypertrophy, focal and segmental glomerular sclerosis, tubular atrophy and interstitial fibrosis. Gene delivery of eNOS, but not β-gal, prevented an increase in systolic blood pressure and proteinuria, and a reduction in plasma and urine NO(2)/NO(3). eNOS gene delivery also reduced a rise in serum creatinine, urinary ET-1 excretion and renal cortex ET-1 levels, and the renal vascular, glomerular and tubular injury. CONCLUSION This study indicates that eNOS gene delivery in rats with renal failure improves NO release, which likely prevents the aggravation of hypertension and slows down the progression of renal failure and injury.
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Affiliation(s)
- Sébastien Savard
- Division of Nephrology and Hypertension, CHUQ Research Centre, L'Hôtel-Dieu de Québec Hospital and Department of Medicine, Université Laval, Quebec, Canada
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Neerhof MG, Synowiec S, Khan S, Thaete LG. Impact of endothelin A receptor antagonist selectivity in chronic nitric oxide synthase inhibition-induced fetal growth restriction in the rat. Hypertens Pregnancy 2010; 29:284-93. [PMID: 20504166 DOI: 10.3109/10641950902777739] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
OBJECTIVE Endothelin receptor A (ETA) antagonism improves fetal and placental growth and placental perfusion on days 1 and 4, but not day 7 of a 7-day infusion of a nitric oxide synthase (NOS) inhibitor. Our purpose was to evaluate the significance of the degree of ETA antagonist selectivity on uteroplacental perfusion and fetal growth on day 7 of chronic NOS inhibition. METHODS Timed-pregnant rats were treated with the NOS inhibitor nitro-L-arginine methyl ester (L-NAME, 2.5 mg/kg/h) with and without one of the following ETA antagonists or their respective vehicles for 7 days beginning on day 14 of gestation: A-127722 (2,000-fold selective for ETA over ETB), FR139317 (8,000-fold ETA-selective), or ABT-546 (28,000-fold ETA-selective). Uterine and placental perfusion, as well as fetal and placental weight, was evaluated at the 7th day of treatment (gestation day 21). RESULTS L-NAME administration resulted in a significant reduction in uterine and placental perfusion as well as fetal and placental growth. In the setting of NOS inhibition, ETA antagonism did not improve uterine or placental perfusion or fetal growth after 7 days of infusion irrespective of the degree of selectivity of the antagonist used. CONCLUSIONS ETA antagonism, irrespective of the degree of receptor selectivity, does not improve fetal growth or uteroplacental perfusion on day 7 of chronic NOS inhibition.
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Affiliation(s)
- Mark G Neerhof
- Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, North Shore University Health System, Evanston, Illinois 60201, USA. mneerhof@ enh.org
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Colombo PC, Onat D, Sabbah HN. Acute heart failure as "acute endothelitis"--Interaction of fluid overload and endothelial dysfunction. Eur J Heart Fail 2008; 10:170-5. [PMID: 18279772 DOI: 10.1016/j.ejheart.2007.12.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Accepted: 12/12/2007] [Indexed: 02/07/2023] Open
Affiliation(s)
- Paolo C Colombo
- Department of Medicine, Division of Cardiology, Columbia University, New York, New York 10032, USA.
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Abstract
The kidney is a remarkable organ whose functions include maintaining fluid and electrolyte balance, excreting metabolic waste products, and controlling vascular tone. Blood flow within the kidney is very heterogeneous, which places the metabolically active medulla at high risk for ischemic injury. A number of mediators play a role in the modulation of renal blood flow, including angiotensin II, dopamine, vasopressin, prostaglandins, atrial natriuretic peptide, endothelin, and nitric oxide. Early markers of renal injury elicit strong interest, although currently there is no reliable marker available. Surgery causes the release of catecholamines, renin, angiotensin, and AVP that lead to a redistribution of renal blood flow and a decrease in GFR. Additionally, general anesthesia often results in some degree of hypotension and depressed cardiac output, which further reduces renal perfusion and potentially jeopardizes renal function. A careful anesthetic plan is imperative in the patient with renal insufficiency or failure because acute renal failure in the perioperative period is associated with a high morbidity and mortality. Factors including advanced age, diabetes, underlying renal insufficiency, and heart failure place a patient at high risk for developing acute renal failure. It is imperative to maintain euvolemia, normotension, and cardiac output, and to avoid nephrotoxic agents to optimize renal blood flow and renal perfusion as the best prevention of renal dysfunction. Further studies are needed to establish if any therapies exist to prevent or treat renal dysfunction effectively.
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Affiliation(s)
- Gebhard Wagener
- Department of Anesthesiology, College of Physicians and Surgeons at Columbia University, New York Presbyterian Hospital, Ph-5, 633 W. 168th Street, New York, NY 10032, USA
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Toda N, Ayajiki K, Okamura T. Interaction of Endothelial Nitric Oxide and Angiotensin in the Circulation. Pharmacol Rev 2007; 59:54-87. [PMID: 17329548 DOI: 10.1124/pr.59.1.2] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Discovery of the unexpected intercellular messenger and transmitter nitric oxide (NO) was the highlight of highly competitive investigations to identify the nature of endothelium-derived relaxing factor. This labile, gaseous molecule plays obligatory roles as one of the most promising physiological regulators in cardiovascular function. Its biological effects include vasodilatation, increased regional blood perfusion, lowering of systemic blood pressure, and antithrombosis and anti-atherosclerosis effects, which counteract the vascular actions of endogenous angiotensin (ANG) II. Interactions of these vasodilator and vasoconstrictor substances in the circulation have been a topic that has drawn the special interest of both cardiovascular researchers and clinicians. Therapeutic agents that inhibit the synthesis and action of ANG II are widely accepted to be essential in treating circulatory and metabolic dysfunctions, including hypertension and diabetes mellitus, and increased availability of NO is one of the most important pharmacological mechanisms underlying their beneficial actions. ANG II provokes vascular actions through various receptor subtypes (AT1, AT2, and AT4), which are differently involved in NO synthesis and actions. ANG II and its derivatives, ANG III, ANG IV, and ANG-(1-7), alter vascular contractility with different mechanisms of action in relation to NO. This review article summarizes information concerning advances in research on interactions between NO and ANG in reference to ANG receptor subtypes, radical oxygen species, particularly superoxide anions, ANG-converting enzyme inhibitors, and ANG receptor blockers in patients with cardiovascular disease, healthy individuals, and experimental animals. Interactions of ANG and endothelium-derived relaxing factor other than NO, such as prostaglandin I2 and endothelium-derived hyperpolarizing factor, are also described.
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Affiliation(s)
- Noboru Toda
- Department of Pharmacology, Shiga University of Medical Science, Seta, Otsu, Japan.
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10
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Abstract
PURPOSE OF REVIEW The balance of angiotensin II and nitric oxide determines the sensitivity of the tubuloglomerular feedback mechanism, renal vascular resistance and filtration rate. Angiotensin II induces nitric oxide release, but the role of angiotensin II receptors here is not fully understood. Further, the angiotensin II-nitric oxide interaction can be modulated by reactive oxygen species. This review focuses on the angiotensin II-nitric oxide interaction and their modulation by reactive oxygen species in the control of renal blood flow. RECENT FINDINGS Ideas about the role of angiotensin II type 1 and angiotensin II type 2 receptors are extended by the observation of angiotensin II type 1-mediated nitric oxide release with direct effects on vascular tone, tubuloglomerular feedback and sympathetic neurotransmission. Angiotensin receptors elicit disparate effects on intrarenal circulation. Angiotensin II-nitric oxide interactions are modulated by reactive oxygen species, as shown by angiotensin II type 1-mediated activation of superoxide and depression of antioxidant enzymes leading to reduced nitric oxide concentration - mechanisms that may be also important in angiotensin II-dependent hypertension. SUMMARY Recent studies show that angiotensin II stimulates the nitric oxide system via angiotensin II type 1 and angiotensin II type 2 receptors, whereas receptors exert different effects on renal and medullary flow. The interaction via angiotensin II type 1 is modulated by reactive oxygen species.
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Affiliation(s)
- Andreas Patzak
- Johannes-Müller-Institute of Physiology, Humboldt-University of Berlin, University Hospital Charité, Berlin, Germany
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Leite-Moreira AF, Castro-Chaves P, Pimentel-Nunes P, Lima-Carneiro A, Guerra MS, Soares JB, Ferreira-Martins J. Angiotensin II acutely decreases myocardial stiffness: a novel AT1, PKC and Na+/H+ exchanger-mediated effect. Br J Pharmacol 2006; 147:690-7. [PMID: 16415904 PMCID: PMC1751345 DOI: 10.1038/sj.bjp.0706659] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Acute effects of angiotensin II (AngII) on diastolic properties of the myocardium were investigated. Increasing concentrations of AngII (10(-9) to 10(-5) M) were added to rabbit papillary muscles in the absence (n=11) or presence of: (i) AT1 receptor antagonists, losartan (10(-6) M; n=7) or ZD-7155 (10(-7) M; n=8); (ii) ZD-7155 (10(-7) M) plus AT2 receptor antagonist PD-123,319 (2 x 10(-6) M; n=6); (iii) PKC inhibitor, chelerythrine (10(-5) M; n=8); or (iv) Na(+)/H(+) exchanger (NHE) inhibitor, 5-(N-methyl-N-isobutyl)-amiloride (10(-6) M; n=10). Passive length-tension relations were constructed before and after a single concentration of AngII (10(-5) M, n=6). Effects of AngII infusion (10 microg kg(-1) min(-1)) were evaluated in in situ rabbit hearts. AngII concentration dependently increased inotropy and resting muscle length (RL). At 10(-5) M, active tension increased 43.3+/-6.25% and RL 1.96+/-0.4%. Correcting RL to its initial value resulted in a 46+/-4% decrease of resting tension, indicating decreased muscle stiffness, as confirmed by the right and downward shift of the passive length-tension relation promoted by AngII. In the intact heart, at matched systolic pressures of 112 mmHg, AngII decreased end-diastolic pressures from 10.3+/-0.3 to 5.9+/-0.5 mmHg, and minimal diastolic pressures from 8.4+/-0.5 to 4.6+/-0.6 mmHg. AT1 blockade inhibited AngII effects on myocardial inotropy and stiffness, while PKC or NHE inhibition only significantly attenuated its effects on resting length and tension. In conclusion, AngII decreases myocardial stiffness, an effect that requires AT1 receptor activation and is mediated by PKC and NHE. This represents a novel mechanism of acute neurohumoral modulation of diastolic function, suggesting that AngII is a powerful regulator of cardiac filling.
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Affiliation(s)
- Adelino F Leite-Moreira
- Department of Physiology, Faculty of Medicine, University of Porto, Porto 4200-319, Portugal.
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Srivastava K, Narang R, Das S, Das N. Nitric oxide and cell adhesion molecules in essential hypertension: a case control study. J Hum Hypertens 2006; 20:537-9. [PMID: 16625236 DOI: 10.1038/sj.jhh.1002034] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Patzak A, Lai E, Persson PB, Persson AEG. ANGIOTENSIN II-NITRIC OXIDE INTERACTION IN GLOMERULAR ARTERIOLES. Clin Exp Pharmacol Physiol 2005; 32:410-4. [PMID: 15854150 DOI: 10.1111/j.1440-1681.2005.04203.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
1. Resistance changes of the afferent and efferent arterioles determine blood flow and filtration rate in the kidney. The tone of both vessels results from the influence of nerves and humoral and paracrine factors, through a balance of constrictor and dilator systems. Angiotensin (Ang) II and nitric oxide (NO) are important factors determining vascular tone. 2. In the present review, we show that, in addition to the basal production of NO, a specific and significant AngII-induced release of NO occurs in glomerular arterioles. Data from investigations of arteriolar contraction, as well as from fluorescence measurements of NO, in the presence of selective angiotensin AT(1) and AT(2) receptor antagonists indicate an AT(1) receptor-stimulated release of NO in afferent arterioles. 3. The AngII-induced liberation of NO could prevent glomerular arterioles from a marked constriction, particularly in situations of high AngII levels in the kidney.
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Affiliation(s)
- Andreas Patzak
- Johannes-Müller-Institute of Physiology, Humboldt-University of Berlin, University Hospital Charité, Berlin, Germany.
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Thaete LG, Kushner DM, Dewey ER, Neerhof MG. Endothelin and the regulation of uteroplacental perfusion in nitric oxide synthase inhibition-induced fetal growth restriction. Placenta 2005; 26:242-50. [PMID: 15708126 DOI: 10.1016/j.placenta.2004.06.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/10/2004] [Indexed: 11/21/2022]
Abstract
The vasoactive mediators nitric oxide and endothelin are both produced in and active in the uterine and placental vasculature. Inhibition of nitric oxide synthase (NOS) results in fetal growth restriction. Endothelin (ET-1) is upregulated in the setting of NOS inhibition. Our purpose was to determine the impact of ET-1 on uterine and placental perfusion in the pregnant rat treated with a NOS inhibitor. Timed-pregnant Sprague-Dawley rats were treated with L-NAME (2.5 mg/kg/h), with and without A-127722 (10 mg/kg/day), or their respective vehicles, for 1, 4, or 7 days beginning on day 14 of gestation. Blood flow to various organs was determined by microsphere infusion. Maternal and fetal plasma nitrate/nitrite (NOx) was determined by fluorometric assay. Uterine and placental perfusion was significantly decreased by NOS inhibition and was restored to normal by ETA antagonism at 1 and 4 days of infusion but not at 7 days. Maternal plasma NOx, but not fetal plasma NOx, was significantly decreased by NOS inhibition alone. ETA antagonism in combination with NOS inhibition significantly lowered fetal plasma NOx. These results indicate that ET-1 is an important regulator of uterine and placental perfusion in the NOS inhibition model of fetal growth restriction. Our results also suggest that maternal administration of L-NAME does not result in significant transport of L-NAME across the placenta, but that addition of an ETA antagonist results in increased placental perfusion, allowing L-NAME greater access to the fetal compartment.
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Affiliation(s)
- L G Thaete
- Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
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Ajayi AA, Hercule H, Cory J, Hayes BE, Oyekan AO. Gender difference in vascular and platelet reactivity to thromboxane A(2)-mimetic U46619 and to endothelial dependent vasodilation in Zucker fatty (hypertensive, hyperinsulinemic) diabetic rats. Diabetes Res Clin Pract 2003; 59:11-24. [PMID: 12482637 DOI: 10.1016/s0168-8227(02)00180-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We examined the hypothesis that gender differences exist in platelet and vascular reactivity in type-2 diabetes mellitus, using Zucker fatty diabetic rats of both sexes and their lean littermates. Type-2 diabetes is characterized by excessive platelet production of TXA(2), which is thrombogenic. Testosterone up-regulates platelet TXA(2) receptors and the aggregation response to thromboxane mimetics. Conversely, estrogen increases vascular nitric oxide (NO) production and inhibits platelet aggregation. Hemodynamic studies were undertaken with the determination of dose-response curve for MAP and renal cortical blood flow (RCF) in response to U46619, angiotensin-II, phenylephrine and endothelin-1, as well as the systemic hemodynamic response to acetylcholine and L-NG nitro-arginine methylester (L-NAME). Platelet aggregation response was evaluated using whole blood impedance aggregometry. There were significant gender differences in the systemic blood pressure and RCF response to TXA(2)-mimetic U46619 and angiotensin-II (P<0.02, ANOVA) but not to phenylephrine or endothelin-1. Male rats exhibited a paradoxical hypotensive response to U46619 (-18+/-11 mmHg) compared with a peak pressor response of +6+/-1 mmHg in female rats (P<0.01, ANOVA). The male rats exhibited an attenuated systemic vasodilator response (P<0.001, ANOVA) to acetylcholine (fall in MAP in male diabetic rats being -24+/-8 mmHg, compared with a fall of -50+/-8 mmHg in females), but a greater rise in the renal cortical resistance in response to NO inhibition by L-NAME (P<0.03) compared with the female rats. Both the slope (46+/-2) and the peak magnitude of the U46619-induced whole blood platelet aggregation (13+/-1) ohms were significantly higher (P<0.01, ANOVA) in male (n=10) compared with female diabetic rats (n=8) (29+/-0.8 slope, 10.0+/-0.8 ohms, respectively). Thus, the male diabetic Zucker rats exhibited an impaired response to vasoconstrictors (U46619 and angiotensin-II) and to endothelial (NO)-mediated vasodilation. The male gender may therefore be associated with the greater prothrombotic activity and a worse impairment of endothelial reactivity in the type-2 diabetic state.
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Affiliation(s)
- A A Ajayi
- Center for Cardiovascular Diseases, Texas Southern University, 3100 Cleburne Avenue, Houston, TX 77004, USA.
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Thomsen K, Nielsen CB, Flyvbjerg A. Effects of glycine on glomerular filtration rate and segmental tubular handling of sodium in conscious rats. Clin Exp Pharmacol Physiol 2002; 29:449-54. [PMID: 12010191 DOI: 10.1046/j.1440-1681.2002.03683.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Infusion of the amino acid glycine leads to an increase in effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) by a mechanism that possibly involves stimulation of nitric oxide (NO). Because NO also increases proximal tubular fluid output (Vprox) by inhibition of proximal tubular Na+ reabsorption and modulation of the tubuloglomerular feedback system, we hypothesized that glycine would increase Vprox as measured by lithium clearance (CLi). 2. In the first series of experiments, the effect of glycine infusion (4 mg/min) was examined in conscious, unstressed, chronically catheterized rats. In an additional series of experiments, the effect of glycine was examined under similar conditions in rats pretreated with a NO synthase (NOS) inhibitor (NG-nitro-L-arginine methyl ester (L-NAME), 2.5 microg/min). 3. Glycine significantly increased ERPF (from 3268 to 4018 microL/min per 100 g bodyweight (BW)), GFR (from 874 to 1009 microL/min per 100 g BW), CLi (from 275 to 461 microL/min per 100 g BW) and Na+ clearance (CNa; from 2.9 to 14.0 microL/min per 100 g BW). Fractional excretion of lithium (FELi; from 32 to 46%) and CNa/CLi (from 0.99 to 2.99%) also rose, indicating inhibition of proximal and distal nephron Na+ reabsorption, respectively. In the rats pretreated with L-NAME, similar haemodynamic and tubular responses to glycine infusion were seen, suggesting that the effects were not mediated by NO. 4. We conclude, that glycine increases ERPF and GFR and it also inhibits proximal and distal nephron Na+ reabsorption leading to an increase in CLi and CNa. There was no indication that any of these effects were mediated by NO.
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Affiliation(s)
- Klaus Thomsen
- Institute for Basic Psychiatric Research, Department of Biological Psychiatry, Risskov, Denmark.
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Wang L, Kubodera S, Araki I, Ueno A, Takeda M. Nitric oxide synthesis and nitric oxide synthase expression in the kidney of rats treated by FK506. Nephrology (Carlton) 2002. [DOI: 10.1046/j.1440-1797.2002.00073.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Just A, Ehmke H, Toktomambetova L, Kirchheim HR. Dynamic characteristics and underlying mechanisms of renal blood flow autoregulation in the conscious dog. Am J Physiol Renal Physiol 2001; 280:F1062-71. [PMID: 11352846 DOI: 10.1152/ajprenal.2001.280.6.f1062] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The time course of the autoregulatory response of renal blood flow (RBF) to a step increase in renal arterial pressure (RAP) was studied in conscious dogs. After RAP was reduced to 50 mmHg for 60 s, renal vascular resistance (RVR) decreased by 50%. When RAP was suddenly increased again, RVR returned to baseline with a characteristic time course (control; n = 15): within the first 10 s, it rose rapidly to 70% of baseline ( response 1), thus already comprising 40% of the total RVR response. Thereafter, it increased at a much slower rate until it started to rise rapidly again at 20–30 s after the pressure step ( response 2). After passing an overshoot of 117% at 43 s, RVR returned to baseline values. Similar responses were observed after RAP reduction for 5 min or after complete occlusions for 60 s. When tubuloglomerular feedback (TGF) was inhibited by furosemide (40 mg iv, n = 12), response 1 was enhanced, providing 60% of the total response, whereas response 2 was completely abolished. Instead, RVR slowly rose to reach the baseline at 60 s ( response 3). The same pattern was observed when furosemide was given at a much higher dose (>600 mg iv; n = 6) or in combination with clamping of the plasma levels of nitric oxide ( n = 6). In contrast to RVR, vascular resistance in the external iliac artery after a 60-s complete occlusion started to rise with a delay of 4 s and returned to baseline within 30 s. It is concluded that, in addition to the myogenic response and the TGF, a third regulatory mechanism significantly contributes to RBF autoregulation, independently of nitric oxide. The three mechanisms contribute about equally to resting RVR. The myogenic response is faster in the kidney than in the hindlimb.
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Affiliation(s)
- A Just
- Institut für Physiologie und Pathophysiologie, Universität Heidelberg, D-69120 Heidelberg, Germany.
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