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Barry EF, O'Neill J, Abdulla MH, Johns EJ. The renal excretory responses to acute renal interstitial angiotensin (1-7) infusion in anaesthetised spontaneously hypertensive rats. Clin Exp Pharmacol Physiol 2021; 48:1674-1684. [PMID: 34375480 DOI: 10.1111/1440-1681.13570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/03/2021] [Accepted: 08/06/2021] [Indexed: 11/29/2022]
Abstract
This study investigated the impact of intrarenal angiotensin 1-7 (Ang [1-7]) infusion on renal excretory function in a rat model of hypertension. Eleven-week-old spontaneously hypertensive rats (SHRs, n = 7) and Han Wistar controls (NCR, n = 7) were anaesthetised with sodium pentobarbital (60 mg/kg i.p.) and prepared for the measurement of mean arterial pressure (MAP) and left renal function during renal interstitial infusion of Ang (1-7) (50 ng/min). The kidneys were harvested, the renal cortex and medulla separated, prepared for measurement of Ang II and Ang (1-7) and Western blot determination of AT1 and Mas receptor protein expression. MAP, glomerular filtration rate (GFR), urine flow (UF) and absolute sodium excretion (UNaV) were 109 ± 16 mmHg, 4.4 ± 1.0 mL/min/kg, 102 ± 16 µL/min/kg and 16 ± 3 µmol/min/kg, respectively in the NCR and 172 ± 24 mmHg, 3.4 ± 0.7 mL/min/kg, 58 ± 30 μL/min/kg and 8.6 ± 4.8 μmol/min/kg respectively in the SHR. Ang (1-7) increased UF (31%), UNa V (50%) and fractional sodium excretion (FENa+ ) (22%) in the NCR group (all p < 0.05) but had no effect on GFR in either group. The magnitudes of the Ang (1-7)-induced increases in UF and UNa V were significantly blunted in the SHR group (model × drug p < 0.05). The renal cortical AT1: Mas receptor expression ratio was significantly higher in the SHR group (p < 0.05) but renal Ang II and Ang (1-7) levels were not statistically different between groups. The Ang (1-7)-induced increases in sodium and water excretion were impaired in the SHR group in the context of an unstimulated RAS. The decrease in responsiveness of the SHR kidney to Ang (1-7) appears to be associated with higher levels of AT1 receptor expression in the renal cortex.
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Affiliation(s)
- Elaine F Barry
- Department of Physiology, University College Cork, Cork, Republic of Ireland
| | - Julie O'Neill
- Department of Gastroenterology, Mercy University Hospital, Cork, Republic of Ireland
| | - Mohammed H Abdulla
- Department of Physiology, University College Cork, Cork, Republic of Ireland
| | - Edward J Johns
- Department of Physiology, University College Cork, Cork, Republic of Ireland
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Kemp BA, Howell NL, Keller SR, Gildea JJ, Shao W, Navar LG, Carey RM. Defective Renal Angiotensin III and AT 2 Receptor Signaling in Prehypertensive Spontaneously Hypertensive Rats. J Am Heart Assoc 2020; 8:e012016. [PMID: 31039659 PMCID: PMC6512109 DOI: 10.1161/jaha.119.012016] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Background Previous studies demonstrated that angiotensin (Ang) III, not Ang II, is the predominant endogenous agonist for Ang type‐2 receptor (AT2R)‐induced natriuresis in normal rats, and that hypertensive 12‐week‐old spontaneously hypertensive rats (SHR) lack natriuretic responses to Ang III. This study tested whether prehypertensive SHR already have defective Ang III‐induced natriuresis and determined possible mechanisms. Methods and Results Female and male normotensive 4‐week‐old SHR and Wistar Kyoto rats were studied after 24‐hour systemic AT1R blockade. Left kidneys received 30 minute renal interstitial infusions of vehicle followed by Ang III (3.5, 7.0, 14, and 28 nmol/kg per min; each dose for 30 minutes). Right kidneys received vehicle infusions. In 4‐week‐old Wistar Kyoto rats, renal interstitial Ang III increased urine sodium (Na+) excretion but failed to induce natriuresis in 4‐week‐old SHR. Renal Ang III levels were similar between Wistar Kyoto rats and SHR, making increased Ang III degradation as a possible cause for defective natriuresis in SHR unlikely. In Wistar Kyoto rats, renal interstitial Ang III induced translocation of AT2Rs to apical plasma membranes of renal proximal tubule cells. Simultaneously, Ang III induced retraction of the major Na+ transporter Na+‐H+ exchanger‐3 (NHE‐3) from apical membranes and internalization of Na+/K+ATPase (NKA) from basolateral membranes of renal proximal tubule cells. Consistent with NHE‐3 and NKA retraction, Ang III increased pSer552‐NHE‐3 and decreased pSer23‐NKA. In contrast, in SHR, intrarenal Ang III failed to induce AT2R translocation, NHE‐3 or NKA retraction, pSer552‐NHE‐3 phosphorylation, or pSer23‐NKA dephosphorylation. Conclusions These results indicate impaired Ang III/AT2R signaling as a possible primary defect in prehypertensive SHR. See Editorial Zhuo and Li
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Affiliation(s)
- Brandon A Kemp
- 1 Division of Endocrinology and Metabolism Department of Medicine University of Virginia School of Medicine Charlottesville VA
| | - Nancy L Howell
- 1 Division of Endocrinology and Metabolism Department of Medicine University of Virginia School of Medicine Charlottesville VA
| | - Susanna R Keller
- 1 Division of Endocrinology and Metabolism Department of Medicine University of Virginia School of Medicine Charlottesville VA
| | - John J Gildea
- 2 Department of Pathology University of Virginia School of Medicine Charlottesville VA
| | - Weijian Shao
- 3 Department of Physiology and Hypertension and Renal Center Tulane University School of Medicine New Orleans LA
| | - Luis Gabriel Navar
- 3 Department of Physiology and Hypertension and Renal Center Tulane University School of Medicine New Orleans LA
| | - Robert M Carey
- 1 Division of Endocrinology and Metabolism Department of Medicine University of Virginia School of Medicine Charlottesville VA
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Michel MC, Brunner HR, Foster C, Huo Y. Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease. Pharmacol Ther 2016; 164:1-81. [PMID: 27130806 DOI: 10.1016/j.pharmthera.2016.03.019] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 03/30/2016] [Indexed: 02/07/2023]
Abstract
We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.
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Affiliation(s)
- Martin C Michel
- Dept. Pharmacology, Johannes Gutenberg University, Mainz, Germany; Dept. Translational Medicine & Clinical Pharmacology, Boehringer Ingelheim, Ingelheim, Germany.
| | | | - Carolyn Foster
- Retiree from Dept. of Research Networking, Boehringer Ingelheim Pharmaceuticals Inc., Ridgefield, CT, USA
| | - Yong Huo
- Dept. Cardiology & Heart Center, Peking University First Hospital, Beijing, PR China
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Hafko R, Villapol S, Nostramo R, Symes A, Sabban EL, Inagami T, Saavedra JM. Commercially available angiotensin II At₂ receptor antibodies are nonspecific. PLoS One 2013; 8:e69234. [PMID: 23840911 PMCID: PMC3698141 DOI: 10.1371/journal.pone.0069234] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 06/06/2013] [Indexed: 12/31/2022] Open
Abstract
Commercially available angiotensin II At₂ receptor antibodies are widely employed for receptor localization and quantification, but they have not been adequately validated. In this study, we characterized three commercially available At₂ receptor antibodies: 2818-1 from Epitomics, sc-9040 from Santa Cruz Biotechnology, Inc., and AAR-012 from Alomone Labs. Using western blot analysis the immunostaining patterns observed were different for every antibody tested, and in most cases consisted of multiple immunoreactive bands. Identical immunoreactive patterns were present in wild-type and At₂ receptor knockout mice not expressing the target protein. In the mouse brain, immunocytochemical studies revealed very different cellular immunoreactivity for each antibody tested. While the 2818-1 antibody reacted only with endothelial cells in small parenchymal arteries, the sc-9040 antibody reacted only with ependymal cells lining the cerebral ventricles, and the AAR-012 antibody reacted only with multiple neuronal cell bodies in the cerebral cortex. Moreover, the immunoreactivities were identical in brain tissue from wild-type or At₂ receptor knockout mice. Furthermore, in both mice and rat tissue extracts, there was no correlation between the observed immunoreactivity and the presence or absence of At₂ receptor binding or gene expression. We conclude that none of these commercially available At₂ receptor antibodies tested met the criteria for specificity. In the absence of full antibody characterization, competitive radioligand binding and determination of mRNA expression remain the only reliable approaches to study At₂ receptor expression.
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Affiliation(s)
- Roman Hafko
- Section on Pharmacology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Sonia Villapol
- Centre for Neuroscience and Regenerative Medicine, Bethesda, Maryland, United States of America
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Regina Nostramo
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, New York, United States of America
| | - Aviva Symes
- Centre for Neuroscience and Regenerative Medicine, Bethesda, Maryland, United States of America
- Department of Pharmacology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, United States of America
| | - Esther L. Sabban
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, New York, United States of America
| | - Tadashi Inagami
- Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America
| | - Juan M. Saavedra
- Section on Pharmacology, Division of Intramural Research Programs, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail:
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Rodriguez-Perez AI, Valenzuela R, Joglar B, Garrido-Gil P, Guerra MJ, Labandeira-Garcia JL. Renin angiotensin system and gender differences in dopaminergic degeneration. Mol Neurodegener 2011; 6:58. [PMID: 21846363 PMCID: PMC3169490 DOI: 10.1186/1750-1326-6-58] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Accepted: 08/16/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND There are sex differences in dopaminergic degeneration. Men are approximately two times as likely as premenopausal women of the same age to develop Parkinson's disease (PD). It has been shown that the local renin angiotensin system (RAS) plays a prominent role in sex differences in the development of chronic renal and cardiovascular diseases, and there is a local RAS in the substantia nigra and dopaminergic cell loss is enhanced by angiotensin via type 1 (AT1) receptors. RESULTS In the present study, we observed that intrastriatal injection of 6-hydroxydopamine induced a marked loss of dopaminergic neurons in the substantia nigra of male rats, which was significantly higher than the loss induced in ovariectomized female rats given estrogen implants (i.e. rats with estrogen). However, the loss of dopaminergic neurons was significantly lower in male rats treated with the AT1 antagonist candesartan, and similar to that observed in female rats with estrogen. The involvement of the RAS in gender differences in dopaminergic degeneration was confirmed with AT1a-null mice lesioned with the dopaminergic neurotoxin MPTP. Significantly higher expression of AT1 receptors, angiotensin converting enzyme activity, and NADPH-oxidase complex activity, and much lower levels of AT2 receptors were observed in male rats than in female rats with estrogen. CONCLUSIONS The results suggest that brain RAS plays a major role in the increased risk of developing PD in men, and that manipulation of brain RAS may be an efficient approach for neuroprotective treatment of PD in men, without the feminizing effects of estrogen.
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Affiliation(s)
- Ana I Rodriguez-Perez
- Department of Morphological Sciences, Networking Research Center on Neurodegenerative Diseases (CIBERNED), University of Santiago de Compostela, Santiago de Compostela, E-15782 Spain
| | - Rita Valenzuela
- Department of Morphological Sciences, Networking Research Center on Neurodegenerative Diseases (CIBERNED), University of Santiago de Compostela, Santiago de Compostela, E-15782 Spain
| | - Belen Joglar
- Department of Morphological Sciences, Networking Research Center on Neurodegenerative Diseases (CIBERNED), University of Santiago de Compostela, Santiago de Compostela, E-15782 Spain
| | - Pablo Garrido-Gil
- Department of Morphological Sciences, Networking Research Center on Neurodegenerative Diseases (CIBERNED), University of Santiago de Compostela, Santiago de Compostela, E-15782 Spain
| | - Maria J Guerra
- Department of Morphological Sciences, Networking Research Center on Neurodegenerative Diseases (CIBERNED), University of Santiago de Compostela, Santiago de Compostela, E-15782 Spain
| | - Jose L Labandeira-Garcia
- Department of Morphological Sciences, Networking Research Center on Neurodegenerative Diseases (CIBERNED), University of Santiago de Compostela, Santiago de Compostela, E-15782 Spain
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Kim BR, Park JH, Kim SH, Cho KJ, Chang MJ. Antihypertensive Properties of Dried Radish Leaves Powder in Spontaneously Hypertensive Rats. ACTA ACUST UNITED AC 2010. [DOI: 10.4163/kjn.2010.43.6.561] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Bo Ram Kim
- Department of Food & Nutrition, Kookmin University, Seoul 136-702, Korea
| | - Ji Ho Park
- Department of Food & Nutrition, Kookmin University, Seoul 136-702, Korea
| | - Sun-Hee Kim
- Department of Food & Nutrition, Kookmin University, Seoul 136-702, Korea
| | - Kang Jin Cho
- Department of Functional Food & Nutrition Division, Rural National Academy of Agricultural Science, Suwon 441-707, Korea
| | - Moon-Jeong Chang
- Department of Food & Nutrition, Kookmin University, Seoul 136-702, Korea
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Padia SH, Howell NL, Kemp BA, Fournie-Zaluski MC, Roques BP, Carey RM. Intrarenal aminopeptidase N inhibition restores defective angiontesin II type 2-mediated natriuresis in spontaneously hypertensive rats. Hypertension 2009; 55:474-80. [PMID: 19996063 DOI: 10.1161/hypertensionaha.109.144956] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
The preferred ligand of angiotensin (Ang) II type 2 (AT(2)R)-mediated natriuresis is Ang III. The major enzyme responsible for the metabolism of Ang III is aminopeptidase N, which is selectively inhibited by compound PC-18. In this study, urine sodium excretion rates (U(Na)V), fractional excretion of sodium, fractional excretion of lithium, glomerular filtration rate, and mean arterial pressures were studied in prehypertensive and hypertensive spontaneously hypertensive rats (SHRs) and compared with age-matched Wistar-Kyoto rats (WKYs). Although renal interstitial infusion of Ang II type 1 receptor blocker candesartan increased U(Na)V in WKYs from a baseline of 0.05+/-0.01 to 0.17+/-0.04 micromol/min (P<0.01), identical infusions failed to increase U(Na)V in hypertensive SHRs. Coinfusion of AT(2)R antagonist PD-123319 abolished the natriuretic responses to candesartan in WKYs, indicating an AT(2)R-mediated effect. AT(2)R-mediated natriuresis was enabled in hypertensive SHRs by inhibiting the metabolism of Ang III with PC-18 (0.05+/-0.01 to 0.11+/-0.03 micromol/min; P<0.05). The defects in sodium excretion were present before the onset of hypertension in SHRs, because young WKYs demonstrated double the U(Na)V of SHRs (0.04+/-0.006 versus 0.02+/-0.003 micromol/min; P<0.01) at baseline. The increased U(Na)V of young WKYs was attributed to reduced renal proximal tubule sodium reabsorption, because increases in fractional excretion of sodium were paralleled by increases in fractional excretion of lithium. Renal interstitial PC-18 infusion ameliorated defective AT(2)R-mediated natriuresis in young SHRs by increasing fractional excretion of sodium and fractional excretion of lithium without changing the glomerular filtration rate. Thus, increased renal proximal tubule sodium retention is observed before the onset of hypertension in SHRs, and inhibition of the metabolism of Ang III ameliorates this pathophysiologic defect in sodium excretion.
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Affiliation(s)
- Shetal H Padia
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Virginia Health System, Charlottesville, Va 22908-1414, USA.
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Na(+)-ATPase in spontaneous hypertensive rats: possible AT(1) receptor target in the development of hypertension. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:360-6. [PMID: 19560439 DOI: 10.1016/j.bbamem.2009.06.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 06/16/2009] [Accepted: 06/19/2009] [Indexed: 01/01/2023]
Abstract
Clinical and experimental data show an increase in sodium reabsorption on the proximal tubule (PT) in essential hypertension. It is well known that there is a link between essential hypertension and renal angiotensin II (Ang II). The present study was designed to examine ouabain-insensitive Na(+)-ATPase activity and its regulation by Ang II in spontaneously hypertensive rats (SHR). We observed that Na(+)-ATPase activity was enhanced in 14-week-old but not in 6-week-old SHR. The addition of Ang II from 10(-12) to 10(-6) mol/L decreased the enzyme activity in SHR to a level similar to that obtained in WKY. The Ang II inhibitory effect was completely reversed by a specific antagonist of AT(2) receptor, PD123319 (10(-8) mol/L) indicating that a system leading to activation of the enzyme in SHR is inhibited by AT(2)-mediated Ang II. Treatment of SHR with losartan for 10 weeks (weeks 4-14) prevents the increase in Na(+)-ATPase activity observed in 14-week-old SHR. These results indicate a correlation between AT(1) receptor activation in SHR and increased ouabain-insensitive Na(+)-ATPase activity. Our results open new possibilities towards our understanding of the pathophysiological mechanisms involved in the increased sodium reabsorption in PT found in essential hypertension.
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9
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Padia SH, Kemp BA, Howell NL, Gildea JJ, Keller SR, Carey RM. Intrarenal angiotensin III infusion induces natriuresis and angiotensin type 2 receptor translocation in Wistar-Kyoto but not in spontaneously hypertensive rats. Hypertension 2008; 53:338-43. [PMID: 19075092 DOI: 10.1161/hypertensionaha.108.124198] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
In Sprague-Dawley rats, renal angiotensin (Ang) type 2 receptors (AT(2)Rs) mediate natriuresis in response to renal interstitial (RI) D(1)-like receptor stimulation or RI Ang III infusion. After D(1)-like receptor activation, apical membrane (AM) but not total renal proximal tubule cell AT(2)R expression is increased, suggesting that AM AT(2)R translocation may be important for natriuresis. The onset of hypertension in spontaneously hypertensive rats (SHRs) is preceded by defects in renal sodium excretion. The present study examines AT(2)R-mediated natriuresis in response to RI Ang III infusion in Wistar-Kyoto rats (WKYs) and SHRs. WKYs and SHRs received RI Ang III infusion after 24 hours of systemic AT(1)R blockade with candesartan. In WKYs, urine sodium excretion rate increased from 0.043+/-0.01 to 0.191+/-0.06 micromol/min (P<0.05) in response to Ang III infusion, but identical conditions failed to increase the urine sodium excretion rate in SHRs. The increase in the urine sodium excretion rate was blocked by coinfusion of PD-123319, a selective AT(2)R antagonist. On confocal microscopy images, Ang III-infused WKYs demonstrated greater renal proximal tubule cell AM AT(2)R fluorescence intensity compared with SHRs (5385+/-725 versus 919+/-35; P<0.0001), and Western blot analysis demonstrated increased AM (0.050+/-0.003 versus 0.038+/-0.003; P<0.01) but not total cell AT(2)R expression in WKYs. In SHRs, AM AT(2)R expression remained unchanged in response to RI Ang III infusion. Thus, RI Ang III infusion elicits natriuresis and renal proximal tubule cell AT(2)R translocation in WKYs. Identical manipulations fail to induce natriuresis or AT(2)R translocation in SHRs, suggesting that defects in AT(2)R-mediated natriuresis and trafficking may be important to the development of hypertension in SHRs.
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Affiliation(s)
- Shetal H Padia
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Virginia Health System, Charlottesville, VA 22908-1414, USA.
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10
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Sullivan JC. Sex and the renin-angiotensin system: inequality between the sexes in response to RAS stimulation and inhibition. Am J Physiol Regul Integr Comp Physiol 2008; 294:R1220-6. [PMID: 18287217 DOI: 10.1152/ajpregu.00864.2007] [Citation(s) in RCA: 148] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The purpose of this review is to examine sex differences in response to stimulation and inhibition of the renin-angiotensin system (RAS). The RAS plays a prominent role in the development of chronic renal disease, and there are known sex differences not only in the expression level of components of the RAS but also in how males and females respond to perturbations of the RAS. In men, renal injury increases in parallel with increased activation of the RAS, while in women, increases in ANG II do not necessarily translate into increases in renal injury. Moreover, both epidemiological and experimental studies have noted sex differences in the therapeutic benefits following angiotensin-converting enzyme inhibitor and angiotensin receptor blocker treatment. Despite these differences, RAS inhibitors are the most commonly prescribed drugs for the treatment of chronic renal disease, irrespective of sex. This review will examine how males and females respond to stimulation and inhibition of the RAS, with a focus on renal disease.
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Affiliation(s)
- Jennifer C Sullivan
- Vascular Biology Center, Medical College of Georgia, Augusta, GA 30912, USA.
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Felder RA, Jose PA. Mechanisms of disease: the role of GRK4 in the etiology of essential hypertension and salt sensitivity. ACTA ACUST UNITED AC 2006; 2:637-50. [PMID: 17066056 DOI: 10.1038/ncpneph0301] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2005] [Accepted: 07/03/2006] [Indexed: 12/15/2022]
Abstract
Hypertension and salt sensitivity of blood pressure are two conditions the etiologies of which are still elusive because of the complex influences of genes, environment, and behavior. Recent understanding of the molecular mechanisms that govern sodium homeostasis is shedding new light on how genes, their protein products, and interacting metabolic pathways contribute to disease. Sodium transport is increased in the proximal tubule and thick ascending limb of Henle of the kidney in human essential hypertension. This Review focuses on the counter-regulation between the dopaminergic and renin-angiotensin systems in the renal proximal tubule, which is the site of about 70% of total renal sodium reabsorption. The inhibitory effect of dopamine is most evident under conditions of moderate sodium excess, whereas the stimulatory effect of angiotensin II is most evident under conditions of sodium deficit. Dopamine and angiotensin II exert their actions via G protein-coupled receptors, which are in turn regulated by G protein-coupled receptor kinases (GRKs). Polymorphisms that lead to aberrant action of GRKs cause a number of conditions, including hypertension and salt sensitivity. Polymorphisms in one particular member of this family-GRK4-have been shown to cause hyperphosphorylation, desensitization and internalization of a member of the dopamine receptor family, the dopamine 1 receptor, while increasing the expression of a key receptor of the renin-angiotensin system, the angiotensin II type 1 receptor. Novel diagnostic and therapeutic approaches for identifying at-risk subjects, followed by selective treatment of hypertension and salt sensitivity, might center on restoring normal receptor function through blocking the effects of GRK4 polymorphisms.
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Affiliation(s)
- Robin A Felder
- Department of Pathology, Post Office Box 800403, University of Virginia Health Sciences Center, Charlottesville, VA 22908, USA.
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Tikellis C, Cooper ME, Bialkowski K, Johnston CI, Burns WC, Lew RA, Smith AI, Thomas MC. Developmental expression of ACE2 in the SHR kidney: a role in hypertension? Kidney Int 2006; 70:34-41. [PMID: 16710353 DOI: 10.1038/sj.ki.5000428] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The abnormal development of the intrarenal renin-angiotensin system (RAS) is thought contribute to adult-onset hypertension in the spontaneously hypertensive rat (SHR). Angiotensin-converting enzyme 2 (ACE2) is a novel enzyme with complementary actions to that of ACE. Recent studies have shown that ACE2 expression is reduced in the adult SHR. However, its regulation in pre-hypertensive animals is unknown. In this study, we examine the developmental expression of ACE2 in the rodent kidney and its temporal expression, as it relates to the development of hypertension in the SHR model. Kidneys from SHR and normotensive Wistar Kyoto (WKY) rats (n=8-12/group) at birth, 6 weeks of age, and adulthood (80 days) were examined. Gene expression and activity of ACE2 were determined by real-time reverse transcription-polymerase chain reaction and quenched fluorescence assays, respectively. Renal expression was localized by in situ hybridization and immunohistochemistry. The expression and ACE2 activity are significantly increased in the SHR kidney at birth. With the onset of hypertension, the tubular expression of ACE2 falls in SHR compared to WKY and remains reduced in the adult SHR kidney. Glomerular expression is paradoxically increased in the SHR glomerulus. The overall developmental pattern of ACE2 expression in the SHR kidney is also modified, with declining expression over the course of renal development. The developmental pattern of ACE2 expression in the SHR kidney is altered before the onset of hypertension, consistent with the key role of the RAS in the pathogenesis of adult-onset hypertension. Further research is required to distinguish the contribution of these changes to the development and progression of hypertension in this model.
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Affiliation(s)
- C Tikellis
- Baker Heart Research Institute, St Kilda Central, Melbourne, Australia
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Baiardi G, Macova M, Armando I, Ando H, Tyurmin D, Saavedra JM. Estrogen upregulates renal angiotensin II AT1 and AT2 receptors in the rat. ACTA ACUST UNITED AC 2005; 124:7-17. [PMID: 15544836 DOI: 10.1016/j.regpep.2004.06.021] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Revised: 06/16/2004] [Accepted: 06/17/2004] [Indexed: 11/17/2022]
Abstract
We studied renal AT1 and AT2 receptors in male, female, ovariectomized and ovariectomized-estrogen-treated Wistar-Hanover and Wistar-Kyoto rats. AT1 receptors and AT1A receptor mRNA predominated, with no significant differences between males and females. AT2 receptor expression was restricted in female rats to the capsule, the transition zone between outer and inner medulla, the endothelium lining the papilla, and arcuate arteries and veins. There were no AT2 receptors in male rats, while male mice express substantial numbers of estrogen-dependent AT2 receptors. Arcuate arteries and veins expressed AT1B mRNA in males and females, and AT2 mRNA in females only. AT1 receptor and AT2 receptor expression were estrogen-dependent, with increases in AT1 and AT2 receptor expression after estrogen treatment in ovariectomized rats. Estrogen treatment increased prostaglandin E2 (PGE2) and cGMP concentrations in the renal medulla, and eNOS expression in cortical arteries. In rodents, expression of renal Angiotensin II receptor types is estrogen-dependent, with significant species, strain and area differences. Our results support an important role for AT2 receptors in the regulation of renal function and in the protective effects of estrogen in the kidney.
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Affiliation(s)
- Gustavo Baiardi
- Section on Pharmacology, National Institute of Mental Health, National Institutes of Health, 10 Center Drive, MSC 1514, Building 10, Room 2D-57, Bethesda, MD 20892, USA
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14
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Zeng C, Yang Z, Wang Z, Jones J, Wang X, Altea J, Mangrum AJ, Hopfer U, Sibley DR, Eisner GM, Felder RA, Jose PA. Interaction of Angiotensin II Type 1 and D
5
Dopamine Receptors in Renal Proximal Tubule Cells. Hypertension 2005; 45:804-10. [PMID: 15699451 DOI: 10.1161/01.hyp.0000155212.33212.99] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Angiotensin II type 1 (AT
1
) receptor and D
1
and D
3
dopamine receptors directly interact in renal proximal tubule (RPT) cells from normotensive Wistar-Kyoto rats (WKY). There is indirect evidence for a D
5
and AT
1
receptor interaction in WKY and spontaneously hypertensive rats (SHR). Therefore, we sought direct evidence of an interaction between AT
1
and D
5
receptors in RPT cells. D
5
and AT
1
receptors colocalized in WKY cells. Angiotensin II decreased D
5
receptors in WKY cells in a time- and concentration-dependent manner (EC
50
=2.7×10
−9
M; t
1/2
=4.9 hours), effects that were blocked by an AT
1
receptor antagonist (losartan). In SHR, angiotensin II (10
−8
M/24 hours) also decreased D
5
receptors (0.96±0.08 versus 0.72±0.08; n=12) and to the same degree as in WKY cells (1.44±0.07 versus 0.92±0.08). However, basal D
5
receptors were decreased in SHR RPT cells (SHR 0.96±0.08; WKY 1.44±0.07; n=12 per strain;
P
<0.05) and renal brush border membranes of SHR compared with WKY (SHR 0.54±0.16 versus WKY 1.46±0.10; n=5 per strain;
P
<0.05). Angiotensin II decreased AT
1
receptor expression in WKY (1.00±0.04 versus 0.72±0.08; n=8;
P
<0.05) but increased it in SHR (0.96±0.04 versus 1.32±0.08; n=8;
P
<0.05). AT
1
and D
5
receptors also interacted in vivo; renal D
5
receptor protein was higher in mice lacking the AT
1A
receptor (AT
1A
−/−; 1.61±0.31; n=6) than in wild-type littermates used as controls (AT
1A
+/+; 0.81±0.08; n=6;
P
<0.05), and renal cortical AT
1
receptor protein was higher in D
5
receptor null mice than in wild-type littermates (1.18±0.08 versus 0.84±0.07; n=4;
P
<0.05). We conclude that D
5
and AT
1
receptors interact with each other. Altered interactions between AT
1
and dopamine receptors may play a role in the pathogenesis of hypertension.
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MESH Headings
- Angiotensin II/pharmacology
- Animals
- Cells, Cultured
- Drug Interactions
- Kidney Tubules, Proximal/cytology
- Kidney Tubules, Proximal/metabolism
- Mice
- Mice, Inbred Strains
- Mice, Knockout
- Rats
- Rats, Inbred SHR
- Rats, Inbred WKY
- Receptor, Angiotensin, Type 1/deficiency
- Receptor, Angiotensin, Type 1/drug effects
- Receptor, Angiotensin, Type 1/metabolism
- Receptors, Dopamine D1/antagonists & inhibitors
- Receptors, Dopamine D1/deficiency
- Receptors, Dopamine D1/metabolism
- Receptors, Dopamine D5
- Tissue Distribution
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Affiliation(s)
- Chunyu Zeng
- Department of Cardiology, Daping Hospital, Third Military Medical University, Chongqing, P.R. China.
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15
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Armando I, Jezova M, Juorio AV, Terrón JA, Falcón-Neri A, Semino-Mora C, Imboden H, Saavedra JM. Estrogen upregulates renal angiotensin II AT(2) receptors. Am J Physiol Renal Physiol 2002; 283:F934-43. [PMID: 12372768 DOI: 10.1152/ajprenal.00145.2002] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
AT(2) receptors may act in opposition to and in balance with AT(1) receptors, their stimulation having beneficial effects. We found renal AT(2) receptor expression in female mice higher than in male mice. We asked the question of whether such expression might be estrogen dependent. In male, female, ovariectomized, and estrogen-treated ovariectomized mice, we studied renal AT(1) and AT(2) receptors by immunocytochemistry and autoradiography, AT(2) receptor mRNA by RT-PCR, and cAMP, cGMP, and PGE(2) by RIA. AT(1) receptors predominated. AT(2) receptors were present in glomeruli, medullary rays, and inner medulla, and in female kidney capsule. AT(1) and AT(2) receptors colocalized in glomeruli. Female mice expressed fewer glomerular AT(1) receptors. Ovariectomy decreased AT(1) receptors in medullary rays and capsular AT(2) receptors. Estrogen administration normalized AT(1) receptors in medullary rays and increased AT(2) receptors predominantly in capsule and inner medulla, and also in glomeruli, medullary rays, and inner stripe of outer medulla. In medullas of estrogen-treated ovariectomized mice there was higher AT(2) receptor mRNA, decreased cGMP, and increased PGE(2) content. We propose that the protective effects of estrogen may be partially mediated through enhancement of AT(2) receptor stimulation.
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Affiliation(s)
- Ines Armando
- Section on Pharmacology, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA.
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16
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Bonnet F, Candido R, Carey RM, Casley D, Russo LM, Osicka TM, Cooper ME, Cao Z. Renal expression of angiotensin receptors in long-term diabetes and the effects of angiotensin type 1 receptor blockade. J Hypertens 2002; 20:1615-24. [PMID: 12172324 DOI: 10.1097/00004872-200208000-00025] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The aims of this study were to assess the renal expression of angiotensin type 1 (AT1) and type 2 (AT2) receptors in diabetic spontaneously hypertensive rats (SHR) and the effect of AT1 receptor blockade on the expression of these receptors. DESIGN Diabetes was induced by injection of streptozotocin in SHRs. Irbesartan, an AT1 receptor antagonist, was given to diabetic SHRs for 32 weeks (15 mg/kg per day, n = 10). Diabetic (n = 10) and non-diabetic SHRs (n = 10) were studied concurrently. A separate group of control and diabetic Wistar-Kyoto (WKY) rats were also evaluated. METHODS Gene and protein expressions of the AT1 and AT2 receptor were assessed by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry with specific antibodies andin vitro autoradiography with [125I]Sar(1), Ile(8) angiotensin II or [125I]CGP42112B. RESULTS Both AT1 and AT2 receptor mRNA levels in the kidney were reduced in diabetic SHRs compared to non-diabetic SHRs. Immunohistochemistry staining with specific antibodies showed a similar reduction in glomerular and tubulo-interstitial staining for both AT1 and AT2 receptors. Reduced binding for the AT1 and AT2 receptor was found in the kidney of diabetic SHRs. Diabetic SHRs developed albuminuria and had glomerular and tubulo-interstitial injury, which were prevented by treatment with irbesartan. Reduced expression of the AT1 receptor, but not the AT2 receptor, in diabetic SHRs was prevented by treatment with irbesartan. In diabetic WKY rats no such reduction in AT1 expression was observed, although there was a trend for reduced AT2 receptor expression. CONCLUSIONS These findings demonstrated that renal expression of both AT1 and AT2 receptor was reduced in long-term diabetic SHRs and that blockade of the AT1 receptor had disparate effects on expression of angiotensin II receptor subtypes.
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MESH Headings
- Angiotensin Receptor Antagonists
- Animals
- Biphenyl Compounds/therapeutic use
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/genetics
- Diabetes Mellitus, Experimental/metabolism
- Diabetes Mellitus, Experimental/pathology
- Diabetic Nephropathies/genetics
- Diabetic Nephropathies/metabolism
- Diabetic Nephropathies/pathology
- Diabetic Nephropathies/prevention & control
- Gene Expression/drug effects
- Irbesartan
- Kidney/drug effects
- Kidney/metabolism
- Kidney/pathology
- Male
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Inbred SHR
- Rats, Inbred WKY
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/genetics
- Receptors, Angiotensin/metabolism
- Tetrazoles/therapeutic use
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Affiliation(s)
- Fabrice Bonnet
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Centre, Heidelberg West, Victoria 3081, Australia
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17
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Gouldsborough I, Ashton N. Maternal environment alters renal response to angiotensin II in the spontaneously hypertensive rat. Clin Exp Pharmacol Physiol 2001; 28:504-9. [PMID: 11422215 DOI: 10.1046/j.1440-1681.2001.03480.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The level of hypertension displayed by the adult spontaneously hypertensive rat (SHR) may be reduced by 20-30 mmHg if SHR pups are cross-fostered to a normotensive dam at birth (SHRX). The mechanisms involved are largely unknown, but may involve the kidney and the renin-angiotensin system (RAS) because renal responses to angiotensin (Ang) II are enhanced in the SHR and brief blockade of the RAS in the young rat permanently lowers blood pressure in the SHR. Accordingly, the aim of the present study was to investigate the effect of cross-fostering on the renal response to AngII in the SHR. 2. Renal function was studied in anaesthetized 4-week-old SHR, cross-fostered SHRX and control Wistar-Kyoto (WKY) rats. Standard clearance methods were used to investigate the renal haemodynamic and tubular effects of AngII. The nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) was coinfused in some experiments to abolish the counterbalancing effect of nitric oxide. 3. Angiotensin II induced a fall in glomerular filtration rate (GFR) in both SHR and SHRX, but not in WKY rats. This was accompanied by a significant reduction in sodium excretion by SHR but not SHRX pups. This effect appeared to be tubular in origin, because sodium clearance was comparable between the two strains after AngII, but fractional sodium excretion was significantly higher in the SHRX. Coinfusion of the NOS inhibitor L-NAME had little further effect on sodium excretion in SHR and SHRX, but restored GFR in SHRX to levels comparable with those in WKY rats. 4. These data suggest that renal tubular sensitivity to AngII in the SHR can be altered during the early stages of postnatal development, which may contribute to the blood pressure- lowering effect of cross-fostering in the SHR.
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Affiliation(s)
- I Gouldsborough
- School of Biological Sciences, University of Manchester, G.38 Stopford Building, Manchester M13 9PT, United Kingdom
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18
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Saavedra JM, Häuser W, Ciuffo G, Egidy G, Hoe KL, Jöhren O, Sembonmatsu T, Inagami T, Armando I. Increased AT(1) receptor expression and mRNA in kidney glomeruli of AT(2) receptor gene-disrupted mice. Am J Physiol Renal Physiol 2001; 280:F71-8. [PMID: 11133516 DOI: 10.1152/ajprenal.2001.280.1.f71] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The proposed feedback between angiotensin II AT(2) and AT(1) receptors prompted us to study AT(1) receptor expression in kidneys of male AT(2) receptor-gene disrupted mice (agtr2 -/y). In wild-type (agtr2 +/y) mice, AT(1) receptor binding and mRNA is abundant in glomeruli, and AT(1) receptor binding is also high in the inner stripe of the outer medulla. AT(2) receptors are scarce, primarily associated to cortical vascular structures. In agtr2 -/y mice, AT(1) receptor binding and mRNA were increased in the kidney glomeruli, and AT(1) receptor binding was higher in the rest of the cortex and outer stripe of the outer medulla, but not in its inner stripe, indicating different cellular regulation. Although AT(2) receptor expression is very low in male agtr 2 +/y mice, their gene disruption alters AT(1) receptor expression. AT(1) upregulation alone may explain the AT(2) gene-disrupted mice phenotype such as increased blood pressure, higher sensitivity to angiotensin II, and altered renal function. The indirect AT(1)/AT(2) receptor feedback could have clinical significance because AT(1) antagonists are widely used in medical practice.
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MESH Headings
- Angiotensin II/pharmacology
- Animals
- Autoradiography
- Blood Pressure/drug effects
- Crosses, Genetic
- Feedback
- Genotype
- Imidazoles/pharmacology
- Kidney Cortex/blood supply
- Kidney Cortex/metabolism
- Kidney Glomerulus/metabolism
- Kidney Medulla/metabolism
- Losartan/pharmacology
- Male
- Mice
- Mice, Inbred Strains
- Mice, Knockout
- Organ Specificity
- Pyridines/pharmacology
- RNA, Messenger/genetics
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/deficiency
- Receptors, Angiotensin/genetics
- Receptors, Angiotensin/metabolism
- Receptors, Angiotensin/physiology
- Transcription, Genetic
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Affiliation(s)
- J M Saavedra
- Section on Pharmacology, National Institute of Mental Health, Bethesda, Maryland 20892, USA.
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19
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Cao Z, Kelly DJ, Cox A, Casley D, Forbes JM, Martinello P, Dean R, Gilbert RE, Cooper ME. Angiotensin type 2 receptor is expressed in the adult rat kidney and promotes cellular proliferation and apoptosis. Kidney Int 2000; 58:2437-51. [PMID: 11115077 DOI: 10.1046/j.1523-1755.2000.00427.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Angiotensin II (Ang II) is associated with cell proliferation and apoptosis. The role of the angiotensin type 2 receptor (AT2R) in these processes remains controversial. Conventional radioligand binding of 125I-Sar1, Ile8 Ang II in adult kidney has failed to demonstrate the binding for the AT2R. METHODS The presence of the AT2R was explored in adult rat kidney by in vitro and in vivo autoradiography using the selective AT2R radioligand 125I-CGP 42112B. The roles of the angiotensin type 1 receptor (AT1R) and the AT2R in mediating cellular proliferation and apoptosis were assessed using selective AT1R or AT2R antagonists in Ang II-infused Sprague-Dawley (SD) rats. RESULTS 125I-CGP 42112B binding was demonstrated by in vitro and in vivo autoradiography techniques in the glomeruli and proximal tubules of SD rats. This binding could be displaced by Ang II and the AT2R antagonist PD123319 but not by the AT1R antagonist valsartan. Subcutaneous infusion of Ang II for 14 days in eight-week-old SD rats induced proliferation of proximal tubular epithelial cells, as assessed by a twofold increase in proliferating cell nuclear antigen (PCNA)-positive cells and apoptosis, as assessed by a threefold increase in terminal dUTP nick end labeling (TUNEL)-positive cells. The administration of the AT2R antagonist PD123319 or the AT1R antagonist valsartan was associated with attenuation of the increases in both PCNA- and TUNEL-positive cells following Ang II infusion. Ang II infusion was associated with increased osteopontin gene and protein expression, which could be reduced by treatment with either valsartan or PD123319. CONCLUSION These findings indicate that there is significant expression of the AT2R in the adult kidney, and that the AT2R has a role in mediating Ang II-induced proliferation and apoptosis in proximal tubular epithelial cells and expression of osteopontin.
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Affiliation(s)
- Z Cao
- Department of Medicine, University of Melbourne, Austin and Repatriation Medical Center (Repatriation Campus),Heidelberg West, Victoria, Australia
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20
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Abstract
A growing body of evidence supports the concept of fetal programming in cardiovascular disease in man, which asserts that an insult experienced in utero exerts a long-term influence on cardiovascular function, leading to disease in adulthood. However, this hypothesis is not universally accepted, hence animal models may be of value in determining potential physiological mechanisms which could explain how fetal undernutrition results in cardiovascular disease in later life. This review describes two major animal models of cardiovascular programming, the in utero protein-restricted rat and the cross-fostered spontaneously hypertensive rat. In the former model, moderate maternal protein restriction during pregnancy induces an increase in offspring blood pressure of 20-30 mmHg. This hypertensive effect is mediated, in part, by fetal exposure to excess maternal glucocorticoids as a result of a deficiency in placental 11-ss hydroxysteroid dehydrogenase type 2. Furthermore, nephrogenesis is impaired in this model which, coupled with increased activity of the renin-angiotensin system, could also contribute to the greater blood pressure displayed by these animals. The second model discussed is the cross-fostered spontaneously hypertensive rat. Spontaneously hypertensive rats develop severe hypertension without external intervention; however, their adult blood pressure may be lowered by 20-30 mmHg by cross-fostering pups to a normotensive dam within the first two weeks of lactation. The mechanisms responsible for this antihypertensive effect are less clear, but may also involve altered renal function and down-regulation of the renin-angiotensin system. These two models clearly show that adult blood pressure is influenced by exposure to one of a number of stimuli during critical stages of perinatal development.
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Affiliation(s)
- N Ashton
- School of Biological Sciences, University of Manchester, Manchester, UK.
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21
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Abstract
In this review, we attempt to outline the age-dependent interactions of principal systems controlling the structure and function of the cardiovascular system in immature rats developing hypertension. We focus our attention on the cardiovascular effects of various pharmacological, nutritional, and behavioral interventions applied at different stages of ontogeny. Several distinct critical periods (developmental windows), in which particular stimuli affect the further development of the cardiovascular phenotype, are specified in the rat. It is evident that short-term transient treatment of genetically hypertensive rats with certain antihypertensive drugs in prepuberty and puberty (at the age of 4-10 wk) has long-term beneficial effects on further development of their cardiovascular apparatus. This juvenile critical period coincides with the period of high susceptibility to the hypertensive effects of increased salt intake. If the hypertensive process develops after this critical period (due to early antihypertensive treatment or late administration of certain hypertensive stimuli, e.g., high salt intake), blood pressure elevation, cardiovascular hypertrophy, connective tissue accumulation, and end-organ damage are considerably attenuated compared with rats developing hypertension during the juvenile critical period. As far as the role of various electrolytes in blood pressure modulation is concerned, prohypertensive effects of dietary Na+ and antihypertensive effects of dietary Ca2+ are enhanced in immature animals, whereas vascular protective and antihypertensive effects of dietary K+ are almost independent of age. At a given level of dietary electrolyte intake, the balance between dietary carbohydrate and fat intake can modify blood pressure even in rats with established hypertension, but dietary protein intake affects the blood pressure development in immature animals only. Dietary protein restriction during gestation, as well as altered mother-offspring interactions in the suckling period, might have important long-term hypertensive consequences. The critical periods (developmental windows) should be respected in the future pharmacological or gene therapy of human hypertension.
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Affiliation(s)
- J Zicha
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
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22
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Grove KL, Deschepper CF. High salt intake differentially regulates kidney angiotensin IV AT4 receptors in Wistar-Kyoto and spontaneously hypertensive rats. Life Sci 1999; 64:1811-8. [PMID: 10350355 DOI: 10.1016/s0024-3205(99)00123-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Functional angiotensin IV (Ang IV) receptors (denoted AT4) are localized to the outer stripe of the medulla in the rat kidney, and may play a critical role in salt homeostasis. The purpose of this study was to determine if AT4 receptor binding in the kidney is differently regulated in the salt-sensitive spontaneously hypertensive (SH) rat compared to Wistar Kyoto (WKY) controls. AT4 receptor binding was determined using in vitro receptor autoradiography. AT4 receptor binding in the outer stripe of the medulla was similar in WKY and SH rats maintained on a 1% salt diet. A high salt diet (8%) resulted in a statistically significant increase (28%) in AT4 receptor binding in kidneys from WKY rats. However, there was no change in AT4 receptor binding in the kidneys of SH rats fed the same diet. The present data indicate that AT4 binding sites are regulated by salt intake. In addition, regulation of this receptor may be impaired in the kidneys of SH rats, explaining in part the salt-sensitivity of this strain.
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Affiliation(s)
- K L Grove
- MRC Multidisciplinary Research Group on Hypertension, Institut de Recherches Cliniques de Montreal, University of Montreal, Quebec, Canada.
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23
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Healy DP, Song L. Kidney aminopeptidase A and hypertension, part I: spontaneously hypertensive rats. Hypertension 1999; 33:740-5. [PMID: 10024338 DOI: 10.1161/01.hyp.33.2.740] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Tissue and plasma levels of aminopeptidase A (APA), the principal enzyme that hydrolyzes angiotensin II (Ang II) to angiotensin III, were measured in spontaneously hypertensive rats (SHR) and their normotensive control strain at 3 different ages corresponding to prehypertensive (4 weeks), developing (8 weeks), and established (16 weeks) phases of hypertension. Plasma APA activity was significantly but modestly elevated in SHR at all 3 ages compared with normotensive Wistar-Kyoto rats. Likewise, levels of APA in brain, heart, and adrenal gland were generally, but again only moderately, elevated in SHR at all ages. However, a large increase in APA activity was seen within the kidney in which APA levels were elevated 41%, 51%, and 68% in SHR at 4, 8, and 16 weeks of age, respectively. Kidney APA levels were also significantly increased in immunoblots from 8- and 16-week-old SHR. Glomeruli isolated from 16-week-old SHR had 57% higher APA activity and increased immunoreactivity compared with Wistar-Kyoto rats. To determine whether the increase in kidney APA activity in SHR was related to Ang II levels, SHR were treated for 2 weeks with the angiotensin-converting enzyme inhibitor captopril. Captopril treatment reduced blood pressure to normotensive values and resulted in a 25% reduction in kidney APA activity. These results suggest that APA expression in the kidney may be regulated by activity of the renin-angiotensin system. If so, this would further suggest that upregulation of APA during conditions in which Ang II levels were elevated would have a protective effect against Ang II-mediated cardiovascular diseases, whereas a decrease in APA expression or a failure to upregulate would exacerbate such conditions.
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Affiliation(s)
- D P Healy
- Department of Pharmacology, Mount Sinai School of Medicine of the City University of New York, NY, USA.
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24
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Gouldsborough I, Ashton N. Effect of cross-fostering on neonatal sodium balance and adult blood pressure in the spontaneously hypertensive rat. Clin Exp Pharmacol Physiol 1998; 25:1024-31. [PMID: 9888001 DOI: 10.1111/j.1440-1681.1998.tb02178.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
1. The aim of the present study was to compare electrolyte handling in naturally reared neonatal spontaneously hypertensive rats (SHR) with those reared by a Wistar-Kyoto (WKY) rat foster mother (denoted SHRX), as cross-fostering SHR pups to a WKY rat dam lowers adult blood pressure in the SHR. 2. The electrolyte content of WKY rat and SHR dams' milk was determined and electrolyte intake and urinary excretion rates were calculated in both naturally reared and cross-fostered WKY rat and SHR pups. 3. The milk sodium concentration fell in both strains (WKY rat: 31.8 +/- 2.0 to 15.2 +/- 1.2 mmol/L; SHR 31.9 +/- 2.5 to 18.2 +/- 1.6 mmol/L; P < 0.001), as did potassium (P < 0.001), over lactation, but there were no differences between strains. Calcium and magnesium concentrations increased (P < 0.001), although SHR dam's milk contained less calcium (P < 0.001) than that of WKY rat dams during the third week of lactation. 4. Spontaneously hypertensive rat pups ingested less milk (P < 0.05) than WKY rat pups; therefore, their cumulative sodium intake over postnatal days 4-15 was significantly lower than that of WKY rat pups (WKY rat vs SHR: 84.4 +/- 3.6 vs 59.7 +/- 2.6 mumol/g bodyweight, respectively; P < 0.05) and fostered SHRX pups (77.7 +/- 7.0 mumol/g bodyweight; P < 0.05). Potassium and magnesium intakes were comparable between SHR, WKY rat and SHRX pups, but SHR pups ingested significantly less calcium than either WKY rat pups (136.1 +/- 6.4 vs 200.1 +/- 9.5 mumol/g bodyweight, respectively; P < 0.05) or SHRX pups (200.0 +/- 18.0 mumol/g bodyweight; P < 0.05). 5. These data show that the neonatal SHR experiences a period of sodium deficiency during the developmental stage when cross-fostering is effective in lowering blood pressure. This is consistent with the reported up-regulation of the renin-angiotensin system observed in SHR at this time and may have a long-term influence on blood pressure.
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25
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Cheng HF, Wang JL, Vinson GP, Harris RC. Young SHR express increased type 1 angiotensin II receptors in renal proximal tubule. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:F10-7. [PMID: 9458818 DOI: 10.1152/ajprenal.1998.274.1.f10] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A potential role for the renin-angiotensin system (RAS) in the development and/or maintenance of hypertension in the genetic model of rat hypertension, spontaneously hypertensive rats (SHR), has been suggested by studies indicating that treatment of immature animals with angiotensin-converting enzyme (ACE) inhibitors prevents subsequent development of hypertension. Because young SHR also demonstrate RAS-dependent increased sodium retention, we examined proximal tubule type 1 angiotensin II receptor (AT1R) mRNA expression in young (4 wk) or adult (14 wk) SHR compared with age-matched Wistar-Kyoto (WKY) rats. Proximal tubules were isolated by Percoll gradient centrifugation, and AT1R mRNA expression was measured by quantitative reverse transcription-polymerase chain reaction (RT-PCR). At 14 wk, when SHR had established hypertension [mean arterial blood pressure (MAP) of SHR vs. WKY: 145 +/- 6 vs. 85 +/- 5 mmHg, n = 14-15], there were no differences in proximal tubule AT1R mRNA levels [SHR vs. WKY: 79 +/- 14 vs. 72 +/- 14 counts/min (cpm) per cpm mutant AT1R per cpm beta-actin x 10(-6), n = 6; not significant (NS)]. In contrast, in 4 wk SHR, at a time of minimal elevations in blood pressure (MAP: 70 +/- 8 vs. 63 +/- 3), SHR proximal tubule AT1R mRNA levels were 263 +/- 30% that of WKY (143 +/- 18 vs. 60 +/- 11 cpm per cpm of mutant AT1R per cpm beta-actin x 10(-6), n = 8; P < 0.005). We have recently shown that chronic ACE inhibition decreases proximal tubule AT1R expression and have also shown that chronic L-3,4-dihydroxyphenylalamine (L-DOPA) administration inhibits AT1R expression in adult Sprague-Dawley proximal tubule and cultured proximal tubule, and this inhibition is mediated via Gs-coupled DA1 receptors. When 3-wk-old animals were given L-DOPA or captopril for 1 wk, MAP was not altered (70 +/- 8 vs. 60 +/- 4 or 61 +/- 5 mmHg), but proximal tubule AT1R mRNA was no longer significantly different between SHR and WKY (68 +/- 9 vs. 38 +/- 7 or 20 +/- 3 vs. 47 +/- 15 cpm per cpm of mutant AT1R per cpm beta-actin x 10(-6)), due to a significant decrease in proximal tubule AT1R expression in SHR (P < 0.005, compared with untreated SHR). Immunoreactive proximal tubule AT1R expression also was increased in 4 wk SHR and was reversed with captopril or L-DOPA treatment. Therefore, these results indicate that young, but not adult, SHR have increased expression of proximal tubule AT1R and that chronic L-DOPA or captopril treatment decreased the elevated AT1R expression to control levels. These results provide further support for an important role of the RAS in the development of hypertension in SHR.
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MESH Headings
- Angiotensin II/metabolism
- Animals
- Blood Pressure
- Cell Membrane/metabolism
- Gene Expression Regulation, Developmental
- Kidney Tubules, Proximal/metabolism
- Male
- Membrane Proteins/biosynthesis
- Membrane Proteins/isolation & purification
- Mutagenesis, Site-Directed
- Polymerase Chain Reaction
- RNA, Messenger/biosynthesis
- Rats
- Rats, Inbred SHR
- Rats, Inbred WKY
- Receptor, Angiotensin, Type 1
- Receptor, Angiotensin, Type 2
- Receptors, Angiotensin/biosynthesis
- Receptors, Angiotensin/isolation & purification
- Sequence Deletion
- Species Specificity
- Transcription, Genetic
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Affiliation(s)
- H F Cheng
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA
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Abstract
Angiotensin receptors are present in a number of organs and systems including heart, kidney, gonad, and placenta; pituitary and adrenal glands; the peripheral vessels, and the central nervous system. This octapeptide exerts diverse effects that include induction of cell hypertrophy and/or hyperplasia and a stimulation of hormone synthesis and ion transport in the heart, kidney, and adrenal, primarily through type 1 (AT1) receptors. In the kidney, several heterogeneous cell populations--endothelial, epithelial, and vascular--carry AT1 receptors. Some studies suggest that AT2 receptors are also functional, but the cell type carrying this receptor and the nature of its specific function have not been fully elucidated. Although studies indicate that AT1 receptors are affected in response to physiological and pathophysiological manipulations, the functional significance of these modulations remains largely uncertain. Nevertheless, recent human genetic studies indicate that polymorphisms in AT1 receptors, as well as in other angiotensin-related genes, have significant impact on organ remodeling processes of the heart and the kidney.
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Affiliation(s)
- T Matsusaka
- Vanderbilt University Medical Center, Nashville, Tennessee 37232-2584, USA
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