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McArdle Z, Singh R, Bielefeldt-Ohmann H, Moritz K, Schreuder M, Denton K. Brief Early Life Angiotensin Converting Enzyme Inhibition Offers Reno-Protection in Sheep with a Solitary Functioning Kidney at 8 Months of Age. J Am Soc Nephrol 2022; 33:1341-1356. [PMID: 35351818 PMCID: PMC9257814 DOI: 10.1681/asn.2021111534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Accepted: 03/18/2022] [Indexed: 11/03/2022] Open
Abstract
Background: Children born with a solitary functioning kidney (SFK) are predisposed to develop hypertension and kidney injury. Glomerular hyperfiltration and hypertrophy contribute to the pathophysiology of kidney injury. Angiotensin converting enzyme inhibitors (ACEi) can mitigate hyperfiltration and may be therapeutically beneficial in reducing progression of kidney injury in SFK. Methods: SFK was induced in male sheep fetuses at 100 days gestation (term=150 day). Between 4-8 weeks of age, SFK lambs received enalapril (SFK+ACEi; 0.5mg/kg/day, once daily, orally) or vehicle (SFK). At 8 months we examined whether SFK+ACEi reduced elevation in blood pressure (BP) and improved basal kidney function, renal functional reserve (RFR; glomerular filtration rate (GFR) response to combined amino acid and dopamine infusion), GFR response to nitric oxide synthase (NOS) inhibition and basal nitric oxide (NO) bioavailability (basal urinary total nitrate+nitrite (NOx)). Results: SFK+ACEi prevented albuminuria, resulted in lower basal GFR (16%), higher renal blood flow (~22%), and lower filtration fraction ( 35%), but similar BP compared to ~ vehicle-treated SFK sheep. Together with greater recruitment of RFR (~14%) in SFK+ACEi animals than SFK, this indicates reduction in glomerular hyperfiltration-mediated kidney dysfunction. During NOS inhibition, the decrease in GFR ( 14%) was greater among SFK+ACEi than among SFK animals. Increased ( 85%) basal urinary total NOx in SFK+ACEi animals compared to SFK indicates elevated NO bioavailability likely contributing to improvements in kidney function and prevention of albuminuria. Conclusions: Brief and early ACEi in SFK is associated with reduced glomerular hyperfiltration-mediated kidney disease up to 8 months of age in a sheep model.
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Affiliation(s)
- Zoe McArdle
- Z McArdle, Cardiovascular Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Australia
| | - Reetu Singh
- R Singh, Cardiovascular Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Australia
| | - Helle Bielefeldt-Ohmann
- H Bielefeldt-Ohmann, School of Veterinary Science, The University of Queensland, Gatton, Australia
| | - Karen Moritz
- K Moritz, Child Health Research Centre and School of Biomedical Sciences, The University of Queensland, Saint Lucia, Australia
| | - Michiel Schreuder
- M Schreuder, Department of Pediatric Nephrology , Amalia Children's Hospital, Nijmegen, Netherlands
| | - Kate Denton
- K Denton, Cardiovascular Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Clayton, Australia
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Soni H, Peixoto-Neves D, Olushoga MA, Adebiyi A. Pharmacological inhibition of TRPV4 channels protects against ischemia-reperfusion-induced renal insufficiency in neonatal pigs. Clin Sci (Lond) 2019; 133:CS20180815. [PMID: 30988131 PMCID: PMC11250923 DOI: 10.1042/cs20180815] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 03/27/2019] [Accepted: 04/15/2019] [Indexed: 12/20/2022]
Abstract
Renal vasoconstriction, an early manifestation of ischemic acute kidney injury (AKI), results in renal hypoperfusion and a rapid decline in kidney function. The pathophysiological mechanisms that underlie ischemia-reperfusion (IR)-induced renal insufficiency are poorly understood, but possibilities include alterations in ion channel-dependent renal vasoregulation. In the present study, we show that pharmacological activation of TRPV4 channels constricted preglomerular microvessels and elicited renal hypoperfusion in neonatal pigs. Bilateral renal ischemia followed by short-term reperfusion increased TRPV4 protein expression in resistance size renal vessels and TRPV4-dependent cation currents in renal vascular smooth muscle cells (SMCs). Selective TRPV4 channel blockers attenuated IR-induced reduction in total renal blood flow (RBF), cortical perfusion, and glomerular filtration rate (GFR). TRPV4 inhibition also diminished renal IR-induced increase in AKI biomarkers. Furthermore, the level of angiotensin II (Ang II) was higher in the urine of IR- compared with sham-operated neonatal pigs. IR did not alter renal vascular expression of Ang II type 1 (AT1) receptors. However, losartan, a selective AT1 receptor antagonist, ameliorated IR-induced renal insufficiency in the pigs. Blockade of TRPV4 channels attenuated Ang II-evoked receptor-operated Ca2+ entry and constriction in preglomerular microvessels. TRPV4 inhibition also blunted Ang II-induced increase in renal vascular resistance (RVR) and hypoperfusion in the pigs. Together, our data suggest that SMC TRPV4-mediated renal vasoconstriction and the ensuing increase in RVR contribute to early hypoperfusion and renal insufficiency elicited by renal IR in neonatal pigs. We propose that multimodal signaling by renal vascular SMC TRPV4 channels controls neonatal renal microcirculation in health and disease.
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Affiliation(s)
- Hitesh Soni
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, U.S.A
| | - Dieniffer Peixoto-Neves
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, U.S.A
| | - Michael A Olushoga
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, U.S.A
| | - Adebowale Adebiyi
- Department of Physiology, College of Medicine, University of Tennessee Health Science Center, Memphis, TN, U.S.A.
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Vinturache AE, Smith FG. Glomerular and tubular effects of nitric oxide (NO) are regulated by angiotensin II (Ang II) in an age-dependent manner through activation of both angiotensin receptors (AT1Rs and AT2Rs) in conscious lambs. Pflugers Arch 2017; 470:249-261. [PMID: 28861607 DOI: 10.1007/s00424-017-2053-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2017] [Revised: 07/23/2017] [Accepted: 08/02/2017] [Indexed: 01/01/2023]
Abstract
Renin-angiotensin (RAS) and nitric oxide (NO) systems and the balance and interaction between them are considered of primary importance in maintaining fluid and electrolyte homeostasis. It has been suggested that the effects of NO may be modulated at least in part by the angiotensin (Ang) II, yet the roles of angiotensin receptor type 1 (AT1R) and type 2 (AT2R) are not well understood. Even though both Ang II and NO are elevated at birth and during the newborn period, their contribution to the adaptation of the newborn to life after birth as well as their physiological roles during development are poorly understood. The aim of this study was to determine if NO regulation of renal function during postnatal maturation is modulated by Ang II through activation of AT1R or AT2R or both receptors. Glomerular and tubular effects of either AT1R selective antagonist ZD 7155, AT2R selective antagonist PD 123319, and both antagonists ZD 7155 plus PD 123319, were measured in 1- (N = 9) and 6-week-old (N = 13) conscious, chronically instrumented lambs before and after removal of endogenous NO with L-arginine analogue, L-NAME. Two-way analysis of variance (ANOVA) procedures for repeated measures over time with factors age and treatment were used to compare the effects of the treatments on several glomerular and tubular variables in both groups. This study showed that L-NAME infusion after pre-treatment with ATR antagonists did not alter glomerular function in 1- or 6-week-old lambs. NO effects on electrolytes handling along the nephron during postnatal development were modulated by Ang II through AT1R and AT2R in an age-dependent manner. Selective inhibition of AT1R and AT2R increased excretion of Na+, K+, and Cl- in 6- but not in 1-week-old lambs. In 6-week-old lambs, urinary flow rate increased by 200%, free water clearance increased by 50%, and urine osmolality decreased by 40% after L-NAME was added to the pre-treatment with ZD 7155 plus PD 123319. When L-NAME was added either to ZD 7155 or PD 123319, the same trend in the alterations of these variables was observed, albeit to a lower degree. In conclusion, in conscious animals, during postnatal maturation, Ang II modulates the effects of NO on glomerular function, fluid, and electrolyte homeostasis through AT1Rs and AT2Rs in an age-dependent manner. Under physiological conditions, AT2Rs may potentiate the effects of AT1R, providing evidence of a crosstalk between ATRs in modulating NO effects on fluid and electrolyte homeostasis during postnatal maturation. This study provides new insights on the regulation of renal function during early postnatal development showing that, compared with later in life, newborns have impaired capacity to regulate glomerular function, water, and electrolyte balance.
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Affiliation(s)
- Angela E Vinturache
- Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute for Child and Maternal Health, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
| | - Francine G Smith
- Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute for Child and Maternal Health, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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Vinturache AE, Smith FG. Renal effects of angiotensin II in the newborn period: role of type 1 and type 2 receptors. BMC PHYSIOLOGY 2016; 16:3. [PMID: 27090941 PMCID: PMC4835895 DOI: 10.1186/s12899-016-0022-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 04/11/2016] [Indexed: 11/10/2022]
Abstract
BACKGROUND Evidence suggests a critical role for the renin-angiotensin system in regulating renal function during postnatal development. However, the physiological relevance of a highly elevated renin-angiotensin system early in life is not well understood, nor which angiotensin receptors might be involved. This study was designed to investigate the roles of angiotensin receptors type 1 (AT1R) and type 2 (AT2R) in regulating glomerular and tubular function during postnatal development. METHODS The renal effects of the selective antagonist to AT1R, ZD 7155 and to AT2R, PD 1233319 were evaluated in two groups of conscious chronically instrumented lambs aged ~ one week (N = 8) and ~ six weeks (N = 10). Two experiments were carried out in each animal and consisted of the assessment of renal variables including glomerular and tubular function, for 30 min before (Control) and 60 min after infusion of ZD 7155 and PD 123319, respectively. Statistical significance was determined using parametric testing (Student t-test, analysis of variance ANOVA) as appropriate. RESULTS ZD 7155 infusion was associated with a significant decrease in glomerular filtration rate and filtration fraction at one but not six weeks; urinary flow rate decreased significantly in older animals, whereas sodium excretion and free water clearance were not altered. There was an age-dependent effect on potassium handling along the nephron, potassium excretion decreasing after ZD 7155 infusion in younger but not in older lambs. PD 123319 had no significant effects on glomerular filtration rate and tubular function in either age group. CONCLUSIONS These results provide evidence to support an important role for AT1Rs in mediating the renal effects of angiotensin II during postnatal maturation in conscious developing animals. In contrast to a role for AT2Rs later in life, there appears to be no role for AT2Rs in influencing the renal effects of Angiotensin II in the postnatal period.
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Affiliation(s)
- Angela E. Vinturache
- Department of Physiology & Pharmacology; Alberta Children’s Hospital Research Institute for Child and Maternal Health, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive, NW, Calgary, AB T2N 4N1 Canada
| | - Francine G. Smith
- Department of Physiology & Pharmacology; Alberta Children’s Hospital Research Institute for Child and Maternal Health, Cumming School of Medicine, University of Calgary, 3330 Hospital Drive, NW, Calgary, AB T2N 4N1 Canada
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Kim E, Eiby Y, Lumbers E, Boyce A, Gibson K, Lingwood B. Expression of genes of the cardiac and renal renin–angiotensin systems in preterm piglets: is this system a suitable target for therapeutic intervention? Ther Adv Cardiovasc Dis 2015; 9:285-96. [DOI: 10.1177/1753944715578615] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Objectives: The newborn circulating, cardiac and renal renin–angiotensin systems (RASs) are essential for blood pressure control, and for cardiac and renal development. If cardiac and renal RASs are immature this may contribute to cardiovascular compromise in preterm infants. This study measured mRNA expression of cardiac and renal RAS components in preterm, glucocorticoid (GC) exposed preterm, and term piglets. Methods: Renal and cardiac RAS mRNA levels were measured using real-time polymerase chain reaction (PCR). Genes studied were: (pro)renin receptor, renin, angiotensinogen, angiotensin converting enzyme (ACE), ACE2, angiotensin type 1 receptor (AT1R) and angiotensin type 2 receptor (AT2R). Results: All the genes studied were expressed in the kidney; neither renin nor AT2R mRNA were detected in the heart. There were no gestational changes in (pro)renin receptor, renin, ACE or AT1R mRNA levels. Right ventricular angiotensinogen mRNA levels in females were lower in preterm animals than at term, and GC exposure increased levels in male piglets. Renal angiotensinogen mRNA levels in female term piglets were lower than females from both preterm groups, and lower than male term piglets. Left ventricular ACE2 mRNA expression was lower in GC treated preterm piglets. Renal AT2R mRNA abundance was highest in GC treated preterm piglets, and the AT1R/AT2R ratio was increased at term. Conclusions: Preterm cardiac and renal RAS mRNA levels were similar to term piglets, suggesting that immaturity of these RASs does not contribute to preterm cardiovascular compromise. Since preterm expression of both renal and cardiac angiotensin II-AT1R is similar to term animals, cardiovascular dysfunction in the sick preterm human neonate might be effectively treated by agents acting on their RASs.
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Affiliation(s)
- Eleanor Kim
- UQ Centre for Clinical Research, University of Queensland, Brisbane, Australia
| | - Yvonne Eiby
- UQ Centre for Clinical Research, Building 71/918, University of Queensland, Royal Brisbane and Women’s Hospital, Herston, Brisbane 4029, Australia
| | - Eugenie Lumbers
- UQ Centre for Clinical Research, University of Queensland, Brisbane, Australia
- School of Biomedical Sciences and Pharmacy, and Mothers and Babies Research Centre, University of Newcastle, New South Wales, Australia
- Department of Physiology, University of New South Wales, New South Wales, Australia
| | - Amanda Boyce
- Department of Physiology, University of New South Wales, New South Wales, Australia
| | - Karen Gibson
- Department of Physiology, University of New South Wales, New South Wales, Australia
| | - Barbara Lingwood
- UQ Centre for Clinical Research, University of Queensland, Brisbane, Australia
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Vinturache AE, Smith FG. Angiotensin type 1 and type 2 receptors during ontogeny: cardiovascular and renal effects. Vascul Pharmacol 2014; 63:145-54. [DOI: 10.1016/j.vph.2014.11.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 10/23/2014] [Accepted: 11/02/2014] [Indexed: 01/24/2023]
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Brown RD, Hilliard LM, Mirabito KM, Wirth LC, Moritz KM, Evans RG, Denton KM, Denton KM. Reduced sensitivity of the renal vasculature to angiotensin II in young rats: the role of the angiotensin type 2 receptor. Pediatr Res 2014; 76:448-52. [PMID: 25119338 DOI: 10.1038/pr.2014.121] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 05/21/2014] [Indexed: 11/09/2022]
Abstract
BACKGROUND The angiotensin type-2 receptor (AT2R) opposes the vasoconstrictor actions of angiotensin II (AngII) mediated through the angiotensin type-1 receptor (AT1R). Renal AT2R levels are high during fetal life, but decrease significantly during postnatal maturation. To provide insight into the functional role of the AT2R in the kidney during postnatal development, we investigated the effects of AT2R antagonism on cardiovascular responses to AngII in young and adult male rats. METHODS In anesthetized 3- and 6-wk-old male Sprague-Dawley rats, mean arterial pressure (MAP) and renal blood flow (RBF) were measured in response to AngII in the presence of vehicle treatment or AT2R blockade with PD123319. RESULTS The pressor effect of AngII and associated reduction in RBF were significantly less in 3-wk- than 6-wk-old rats. AT2R blockade potentiated the reduction in RBF in response to AngII in 3-wk-old rats only. CONCLUSION In young rats, the AT2R modulates the response to AngII, blunting renal vasoconstriction. This effect is attenuated with age in association with a developmental reduction in renal AT2R expression. These findings may have implications for the development of novel therapies that target the renin-angiotensin system for the improvement of renal function in term and, in particular, preterm infants.
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Affiliation(s)
- Russell D Brown
- Department of Physiology, Monash University, Melbourne, Australia
| | | | | | - Laura C Wirth
- Department of Physiology, Monash University, Melbourne, Australia
| | - Karen M Moritz
- School of Biomedical Sciences, University of Queensland, Brisbane, Australia
| | - Roger G Evans
- Department of Physiology, Monash University, Melbourne, Australia
| | - Kate M Denton
- Department of Physiology, Monash University, Melbourne, Australia
| | - Kate M Denton
- Department of Physiology, Monash University, Melbourne, Australia
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Vinturache AE, Smith FG. Angiotensin receptors modulate the renal hemodynamic effects of nitric oxide in conscious newborn lambs. Physiol Rep 2014; 2:e12027. [PMID: 24872358 PMCID: PMC4098750 DOI: 10.14814/phy2.12027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Revised: 04/28/2014] [Accepted: 05/01/2014] [Indexed: 12/20/2022] Open
Abstract
This study aimed to elucidate the roles of both angiotensin II (ANG II) receptors - type 1 (AT1Rs) and type 2 (AT2Rs) - separately and together in influencing hemodynamic effects of endogenously produced nitric oxide (NO) during postnatal development. In conscious, chronically instrumented lambs aged ~1 week (8 ± 1 days, N = 8) and ~6 weeks (41 ± 2 days, N = 8), systolic, diastolic, and mean arterial pressure (SAP, DAP, MAP) and venous pressure (MVP), renal blood flow (RBF), and renal vascular resistance (RVR) were measured in response to the l-arginine analog, l-NAME after pretreatment with either the AT1R antagonist, ZD 7155, the AT2R antagonist, PD 123319, or both antagonists. The increase in SAP, DAP, and MAP by l-NAME was not altered by either ATR antagonist in either age group. The increase in RBF after l-NAME was, however, altered by both ATR antagonists in an age-dependent manner, which was mediated predominantly through AT2Rs in newborn lambs. These findings reveal that there is an age-dependent interaction between the renin-angiotensin (RAS) and the NO pathway in regulating renal but not systemic hemodynamics through both ATRs, whereas AT2Rs appear to be important in the renal hemodynamic effects of NO early in life.
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Affiliation(s)
- Angela E. Vinturache
- The Alberta Children's Hospital Research Institute for Child and Maternal Health, University of Calgary, Calgary, Alberta, Canada
- The Department of Physiology & Pharmacology, University of Calgary, Calgary, Alberta, Canada
| | - Francine G. Smith
- The Alberta Children's Hospital Research Institute for Child and Maternal Health, University of Calgary, Calgary, Alberta, Canada
- The Department of Physiology & Pharmacology, University of Calgary, Calgary, Alberta, Canada
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Vinturache AE, Smith FG. Do Angiotensin Type 2 Receptors Modulate Haemodynamic Effects of Type 1 Receptors in Conscious Newborn Lambs? J Renin Angiotensin Aldosterone Syst 2014; 15:450-7. [DOI: 10.1177/1470320313506479] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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Ebenezar KK, Wong AKO, Smith FG. Haemodynamic responses to angiotensin II in conscious lambs: role of nitric oxide and prostaglandins. Pflugers Arch 2011; 463:399-404. [DOI: 10.1007/s00424-011-1065-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 11/16/2011] [Accepted: 11/23/2011] [Indexed: 11/25/2022]
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Wehlage SJ, Smith FG. Nitric oxide and angiotensin II regulate cardiovascular homeostasis and the arterial baroreflex control of heart rate in conscious lambs. J Renin Angiotensin Aldosterone Syst 2011; 13:99-106. [DOI: 10.1177/1470320311423282] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
To investigate the potential role of angiotensin II (Ang II) type 1 receptors (AT1Rs) as well as endogenously produced nitric oxide (NO) in regulating cardiovascular homeostasis during ontogeny, experiments were carried out in conscious lambs aged approximately 1 week ( N = 9) and 6 weeks ( N = 11). The arterial baroreflex control of heart rate (HR) was assessed before and after intravenous (IV) infusion of the selective AT1R antagonist, ZD 7155, before and after IV administration of the L-arginine analogue, NG-nitro-L-arginine methyl ester (L-NAME). In both groups, after ZD 7155 alone, mean arterial pressure decreased then increased after L-NAME. At 1 but not 6 weeks, HR decreased after ZD 7155 as well as after L-NAME. At 1 but not 6 weeks, there was a decrease in the HR range after ZD 7155 and after ZD 7155 + L-NAME, as compared to control. There was also a decrease in minimum HR after ZD 7155 + L-NAME at 1 week. These data provide new evidence that, together, Ang II and NO regulate cardiovascular homeostasis as well as the arterial baroreflex of HR early in life which may help to explain the activation of these two systems early in life.
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Affiliation(s)
- Stephanie J Wehlage
- Alberta Children’s Hospital Research Institute for Child and Maternal Health, University of Calgary, Calgary, Alberta, Canada
| | - Francine G Smith
- Alberta Children’s Hospital Research Institute for Child and Maternal Health, University of Calgary, Calgary, Alberta, Canada
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Chappellaz ML, Smith FG. Systemic and renal hemodynamic effects of the AT1 receptor antagonist, ZD 7155, and the AT2 receptor antagonist, PD 123319, in conscious lambs. Pflugers Arch 2006; 453:477-86. [PMID: 17051392 DOI: 10.1007/s00424-006-0148-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2006] [Revised: 07/17/2006] [Accepted: 08/01/2006] [Indexed: 10/24/2022]
Abstract
Experiments were carried out to investigate age- and dose-dependent effects of the selective AT(1) receptor antagonist, ZD 7155, and the selective AT(2) receptor antagonist, PD 123319, on systemic and renal hemodynamics in conscious, chronically instrumented lambs aged approximately 1 and approximately 6 weeks of postnatal life. Mean arterial pressure (MAP), mean venous pressure (MVP), and renal blood flow (RBF) were measured for 10 min before and for 120 min after ZD 7155, PD 123319, or vehicle. In both age groups, administration of ZD 7155 decreased renal vascular resistance (RVR) and increased RBF within 5 min. These responses lasted less than 90 min but were not dose-dependent. MAP decreased by 30 min after administration of ZD 7155 in both age groups at doses >/=400 microg kg(-1); the remaining decreased for up to 120 min, depending upon the dose. Pressor responses to angiotensin II (ANG II) were abolished within 5 min of administration of all doses of ZD 7155, at both 1- and 6 weeks. PD 123319 had no detectable effects on systemic or renal hemodynamics or on the pressor responses to ANG II. Therefore, under physiological conditions in conscious newborn animals, ANG II modulates both resting blood pressure and RVR through activation of AT(1) but not AT(2) receptors.
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MESH Headings
- Angiotensin II/pharmacology
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Angiotensin II Type 2 Receptor Blockers
- Animals
- Animals, Newborn
- Blood Pressure/drug effects
- Consciousness
- Dose-Response Relationship, Drug
- Imidazoles/pharmacology
- Kidney/blood supply
- Kidney/drug effects
- Kidney/metabolism
- Naphthyridines/pharmacology
- Pyridines/pharmacology
- Receptor, Angiotensin, Type 1/metabolism
- Receptor, Angiotensin, Type 1/physiology
- Receptor, Angiotensin, Type 2/metabolism
- Receptor, Angiotensin, Type 2/physiology
- Renal Circulation/drug effects
- Sheep
- Time Factors
- Vascular Resistance/drug effects
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Affiliation(s)
- Mona L Chappellaz
- Department of Physiology & Biophysics, University of Calgary, Calgary, Alberta, T2N 4N1, Canada
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