Search

Background: DNA methylation (DNAm) is associated with gene regulation and estimated glomerular filtration rate (eGFR), a measure of kidney function. Decreased eGFR is more common among US Hispanics and African Americans. The causes for this are poorly understood. We aimed to identify trans-ethnic and ethnic-specific differentially methylated positions (DMPs) associated with eGFR using an agnostic, genome-wide approach., Methods: The study included up to 5428 participants from multi-ethnic studies for discovery and 8109 participants for replication. We tested the associations between whole blood DNAm and eGFR using beta values from Illumina 450K or EPIC arrays. Ethnicity-stratified analyses were performed using linear mixed models adjusting for age, sex, smoking, and study-specific and technical variables. Summary results were meta-analyzed within and across ethnicities. Findings were assessed using integrative epigenomics methods and pathway analyses., Results: We identified 93 DMPs associated with eGFR at an FDR of 0.05 and replicated 13 and 1 DMPs across independent samples in trans-ethnic and African American meta-analyses, respectively. The study also validated 6 previously published DMPs. Identified DMPs showed significant overlap enrichment with DNase I hypersensitive sites in kidney tissue, sites associated with the expression of proximal genes, and transcription factor motifs and pathways associated with kidney tissue and kidney development., Conclusions: We uncovered trans-ethnic and ethnic-specific DMPs associated with eGFR, including DMPs enriched in regulatory elements in kidney tissue and pathways related to kidney development. These findings shed light on epigenetic mechanisms associated with kidney function, bridging the gap between population-specific eGFR-associated DNAm and tissue-specific regulatory context.

Background: More than one-third of US adults have prediabetes, which is typically accompanied by hypertension., Methods: We examined whether prediabetes modified the effects of intensive systolic blood pressure (SBP) lowering on the incidence of chronic kidney disease (CKD) and acute kidney injury (AKI) events in a post-hoc analysis of the Systolic Blood Pressure Intervention Trial (SPRINT). Diabetes was a SPRINT exclusion criterion. We defined normoglycemia and prediabetes as fasting plasma glucose <100 mg/dl and ≥100 mg/dl, respectively., Results: Of the 9,323 participants included in this analysis, 3,898 (41.8%) had prediabetes and the rest (5,425) had normoglycemia. In participants with baseline estimated glomerular filtration rate (eGFR) ≥60 ml/min/1.73 m2, incident CKD was defined as a ≥30% decline in eGFR to below 60 ml/min/1.73 m2 with repeat confirmation. AKI events were identified clinically. In the non-CKD participants (n = 6,678), there were 164 incident CKD events. The hazard ratios (HRs) for incident CKD for intensive SBP goal (<120 mm Hg) vs. standard SBP goal (<140 mm Hg) in the normoglycemia (HR: 3.25, 95% CI: 2.03, 5.19) and prediabetes (HR: 3.90, 95% CI: 2.17, 7.02) groups were similar (interaction P value 0.64). In the entire analytic cohort (N = 9,323), there were 310 AKI events. AKI HRs for intensive vs. standard SBP in the normoglycemia (HR: 1.59, 95% CI: 1.17, 2.15) and prediabetes (HR: 1.74, 95% CI: 1.22, 2.48) groups were also similar (interaction P value 0.71)., Conclusions: Prediabetes was highly prevalent, but there was no evidence that prediabetes modified the effects of SPRINT intervention on kidney events.CLINICAL TRIALS REGISTRATIONNCT01206062., (© Published by Oxford University Press on behalf of American Journal of Hypertension Ltd 2019.)

Chronic kidney disease (CKD) affects ~10% of the global population, with considerable ethnic differences in prevalence and aetiology. We assemble genome-wide association studies of estimated glomerular filtration rate (eGFR), a measure of kidney function that defines CKD, in 312,468 individuals of diverse ancestry. We identify 127 distinct association signals with homogeneous effects on eGFR across ancestries and enrichment in genomic annotations including kidney-specific histone modifications. Fine-mapping reveals 40 high-confidence variants driving eGFR associations and highlights putative causal genes with cell-type specific expression in glomerulus, and in proximal and distal nephron. Mendelian randomisation supports causal effects of eGFR on overall and cause-specific CKD, kidney stone formation, diastolic blood pressure and hypertension. These results define novel molecular mechanisms and putative causal genes for eGFR, offering insight into clinical outcomes and routes to CKD treatment development.

Objective: The aim of this study was to examine the association between BMI categories, stratified by metabolic health status, and the risk of kidney function decline (KFD)., Methods: In this study, 42,128 adult patients with a stable BMI were classified over a 3-year baseline window by BMI and metabolic health status (assessed by Adult Treatment Panel-III criteria). KFD was defined as an estimated glomerular filtration rate (eGFR) decline ≥ 30%, eGFR < 15 mL/min/1.73 m 2 , or receipt of dialysis and/or transplant., Results: Over a median of 5.1 years (interquartile range 2.1-8.9), 6,533 (15.5%) individuals developed KFD. Compared with the normal weight, metabolically healthy category, metabolically healthy obesity was associated with a higher risk of KFD (adjusted hazard ratio [aHR] 1.52; 95% CI: 1.22-1.89). aHRs for KFD were 1.17 (95% CI: 0.89-1.53), 2.21 (95% CI: 1.59-3.08), and 2.20 (95% CI: 1.55-3.11) for metabolically healthy obesity with BMI 30 to 34.9, BMI 35 to 39.9, and BMI ≥ 40 kg/m 2 . These associations were consistent among men and women, patients with eGFR ≥ or < 90 mL/min/1.73 m 2 , and age ≥ or < 55 years. The risk of KFD was highest among metabolically unhealthy individuals with BMI ≥ 40 (aHR 4.02; 95% CI: 3.40-4.75 vs. metabolically healthy individuals with normal weight)., Conclusions: Obesity, whether in the presence or absence of metabolic health, is a risk factor for KFD., (© 2018 The Obesity Society.)

Background: Early addition of endothelin (ET) type A (ET A ) receptor blockade to complex renin-angiotensin system (RAS) blockade has previously been shown to provide better renoprotection against progression of chronic kidney disease (CKD) in Ren-2 transgenic hypertensive rats (TGR) after 5/6 renal ablation (5/6 NX). In this study, we examined if additional protection is provided when ET A blockade is applied in rats with already developed CKD., Methods: For complex RAS inhibition, an angiotensin-converting enzyme inhibitor along with angiotensin II type 1 receptor blocker was used. Alternatively, ET A receptor blocker was added to the RAS blockade. The treatments were initiated 6 weeks after 5/6 NX and the follow-up period was 50 weeks., Results: When applied in established CKD, addition of ET A receptor blockade to the complex RAS blockade brought no further improvement of the survival rate (30% in both groups); surprisingly, aggravated albuminuria (588 ± 47 vs. 245 ± 38 mg/24 h, p < 0.05) did not reduce renal glomerular injury index (1.25 ± 0.29 vs. 1.44 ± 0.26), did not prevent the decrease in creatinine clearance (203 ± 21 vs. 253 ± 17 µl/min/100 g body weight), and did not attenuate cardiac hypertrophy to a greater extent than observed in 5/6 NX TGR treated with complex RAS blockade alone., Conclusions: When applied in the advanced phase of CKD, addition of ET A receptor blockade to the complex RAS blockade brings no further beneficial renoprotective effects on the CKD progression in 5/6 NX TGR, in addition to those seen with RAS blockade alone.

The role of the intrarenal renin-angiotensin system (RAS) in the pathophysiology of malignant hypertension is not fully understood. Accumulating evidence indicates that the recently discovered vasodilator axis of the RAS, angiotensin-converting enzyme (ACE) type 2 (ACE2)/angiotensin 1-7 (ANG 1-7), constitutes an endogenous system counterbalancing the hypertensiogenic axis, ACE/angiotensin II (ANG II)/AT1 receptor. This study aimed to evaluate the role of the intrarenal vasodilator RAS axis in the pathophysiology of ANG II-dependent malignant hypertension in Cyp1a1-Ren-2 transgenic rats. ANG II-dependent malignant hypertension was induced by 13 days' dietary administration of indole-3-carbinol (I3C), a natural xenobiotic that activates the mouse renin gene in Cyp1a1-Ren-2 transgenic rats. It was hypothesized that pharmacologically-induced inhibition of the ACE2/ANG 1-7 complex should aggravate, and activation of this axis should attenuate, the course of ANG II-dependent malignant hypertension. Blood pressure (BP) was monitored by radiotelemetry. ACE2 inhibitor (DX 600, 0.2 μg/day) and ACE2 activator (DIZE, 1 mg/day) were administrated via osmotic minipumps. Even though ACE2 inhibitor significantly decreased and ACE2 activator increased intrarenal ANG 1-7 concentrations, the course of BP, as well as of albuminuria, cardiac hypertrophy and renal glomerular damage, were not altered. It was shown that intrarenal alterations in the ACE2/ANG 1-7 complex did not significantly modify the course of malignant hypertension in I3C-induced Cyp1a1-Ren-2 transgenic rats. Thus, in our experimental setting alterations of this intrarenal vasodilator complex of the RAS do not significantly modify the form of malignant hypertension that clearly depends on the inappropriately increased activity of the ACE/ANG II/AT1 receptor axis., (© 2016 John Wiley & Sons Australia, Ltd.)

The aim of the present study was to test the hypothesis that chronic hypoxia would aggravate hypertension in Ren-2 transgenic rats (TGR), a well-defined monogenetic model of hypertension with increased activity of endogenous renin-angiotensin system (RAS). Systolic blood pressure (SBP) in conscious rats and mean arterial pressure (MAP) in anesthetized TGR and normotensive Hannover Sprague-Dawley (HanSD) rats were determined under normoxia that was either continuous or interrupted by two weeks´ hypoxia. Expression, activities and concentrations of individual components of RAS were studied in plasma and kidney of TGR and HanSD rats under normoxic conditions and after exposure to chronic hypoxia. In HanSD rats two weeks´ exposure to chronic hypoxia did not alter SBP and MAP. Surprisingly, in TGR it decreased markedly SBP and MAP; this was associated with substantial reduction in plasma and kidney renin activities and also of angiotensin II (ANG II) levels, without altering angiotensin-converting enzyme (ACE) activities. Simultaneously, in TGR the exposure to hypoxia increased kidney ACE type 2 (ACE2) activity and angiotensin 1-7 (ANG 1-7) concentrations as compared with TGR under continuous normoxia. Based on these results, we propose that suppression of the hypertensiogenic ACE-ANG II axis in the circulation and kidney tissue, combined with augmentation of the intrarenal vasodilator ACE2-ANG 1-7 axis, is the main mechanism responsible for the blood pressure-lowering effects of chronic hypoxia in TGR.

The aim of the present study was to evaluate the hypothesis that the antihypertensive effects of inhibition of soluble epoxide hydrolase (sEH) are mediated by increased intrarenal availability of epoxyeicosatrienoic acids (EETs), with consequent improvement in renal haemodynamic autoregulatory efficiency and the pressure-natriuresis relationship. Ren-2 transgenic rats (TGR), a model of angiotensin (Ang) II-dependent hypertension, and normotensive transgene-negative Hannover Sprague-Dawley (HanSD) rats were treated with the sEH inhibitor cis-4-(4-(3-adamantan-1-yl-ureido)cyclohexyloxy)benzoic acid (c-AUCB; 26 mg/L) for 48 h. Then, the effects on blood pressure (BP), autoregulation of renal blood flow (RBF) and glomerular filtration rate (GFR), and on the pressure-natriuresis relationship in response to stepwise reductions in renal arterial pressure (RAP) were determined. Treatment with c-AUCB did not significantly change BP, renal autoregulation or pressure-natriuresis in normotensive HanSD rats. In contrast, c-AUCB treatment significantly reduced BP, increased intrarenal bioavailability of EETs and significantly suppressed AngII levels in TGR. However, treatment with c-AUCB did not significantly improve the autoregulatory efficiency of RBF and GFR in response to reductions of RAP and to restore the blunted pressure-natriuresis relationship in TGR. Together, the data indicate that the antihypertensive actions of sEH inhibition in TGR are predominantly mediated via significant suppression of intrarenal renin-angiotensin system activity., (© 2012 The Authors Clinical and Experimental Pharmacology and Physiology © 2012 Wiley Publishing Asia Pty Ltd.)

Objective: The present study was performed to investigate in a model of malignant hypertension if the antihypertensive actions of soluble epoxide hydrolase (sEH) inhibition are nitric oxide (NO)-dependent., Methods: ANG II-dependent malignant hypertension was induced through dietary administration for 3 days of the natural xenobiotic indole-3-carbinol (I3C) in Cyp1a1-Ren-2 transgenic rats. Blood pressure (BP) was monitored by radiotelemetry and treatment with the sEH inhibitor [cis-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyl-oxy]-benzoic acid (c-AUCB)] was started 48 h before administration of the diet containing I3C. In separate groups of rats, combined administration of the sEH inhibitor and the nonspecific NO synthase inhibitor [Nω-nitro-L-arginine methyl ester (L-NAME)] on the course of BP in I3C-induced and noninduced rats were evaluated. In addition, combined blockade of renin-angiotensin system (RAS) was superimposed on L-NAME administration in separate groups of rats. After 3 days of experimental protocols, the rats were prepared for renal functional studies and renal concentrations of epoxyeicosatrienoic acids (EETs) and their inactive metabolites dihydroxyeicosatrienoic acids (DHETEs) were measured., Results: Treatment with c-AUCB increased the renal EETs/DHETEs ratio, attenuated the increases in BP, and prevented the decreases in renal function and the development of renal damage in I3C-induced Cyp1a1-Ren-2 rats. The BP lowering and renoprotective actions of the treatment with the sEH inhibitor c-AUCB were completely abolished by concomitant administration of L-NAME and not fully rescued by double RAS blockade without altering the increased EETs/DHETEs ratio., Conclusion: Our current findings indicate that the antihypertensive actions of sEH inhibition in this ANG II-dependent malignant form of hypertension are dependent on the interactions of endogenous bioavailability of EETs and NO.

Background: The association of subclinical vascular disease and early declines in kidney function has not been well studied., Study Design: Prospective cohort study., Setting & Participants: Multi-Ethnic Study of Atherosclerosis (MESA) participants with estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m(2) with follow-up of 5 years., Predictors: Pulse pressure, small (SAE) and large arterial elasticity (LAE), and flow-mediated dilation., Outcomes: Kidney function decline., Measurements: SAE and LAE were measured by pulse contour analysis of the radial artery. Kidney function was assessed by eGFR based on serum creatinine (eGFR(SCr)) and cystatin C (eGFR(SCysC))., Results: For 4,853 adults, higher pulse pressure and lower SAE and LAE had independent and linear associations with faster rates of kidney function decline. Compared with persons with pulse pressure of 40-50 mm Hg, eGFR(SCysC) declines were 0.29 (P = 0.006), 0.56 (P < 0.001), and 0.91 (P < 0.001) mL/min/1.73 m(2)/y faster in persons with pulse pressure of 50-60, 60-70, and >70 mm Hg, respectively. Compared with the highest quartile of SAE (most elastic), eGFR(SCysC) declines were 0.26 (P = 0.009), 0.35 (P = 0.001), and 0.70 (P < 0.001) mL/min/1.73 m(2)/y faster for the second, third, and fourth quartiles, respectively. For LAE, compared with the highest quartile, eGFR(SCysC) declines were 0.28 (P = 0.004), 0.58 (P < 0.001), and 0.83 (P < 0.001) mL/min/1.73 m(2)/y faster for each decreasing quartile of LAE. Findings were similar for eGFR(SCr). In contrast, for 2,997 adults with flow-mediated dilation and kidney function measures, flow-mediated dilation was not associated significantly with kidney function decline. For every 1-standard deviation greater flow-mediated dilation, eGFR(SCysC) and eGFR(SCr) changed by 0.05 (P = 0.3) and 0.06 mL/min/1.73 m(2)/y (P = 0.04), respectively., Limitations: We had no direct measure of GFR, in common with nearly all large population-based studies., Conclusions: Higher pulse pressure and lower arterial elasticity, but not flow-mediated dilation, were associated linearly and independently with faster kidney function decline in persons with eGFR ≥60 mL/min/1.73 m(2). Future studies should investigate whether treatments to decrease the stiffness of large and small arteries may slow the rate of kidney function loss., (Copyright © 2011 National Kidney Foundation, Inc. All rights reserved.)

Alterations in renal function contribute to Goldblatt two-kidney, one-clip (2K1C) hypertension. A previous study indicated that bioavailability of cytochrome P-450 metabolites epoxyeicosatrienoic acids (EETs) is decreased while that of 20-hydroxyeicosatetraenoic acids (20-HETE) is increased in this model. We utilized the inhibitor of soluble epoxide hydrolase cis-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (c-AUCB) and HET-0016, the inhibitor of 20-HETE production, to study the role of EETs and 20-HETE in the regulation of renal function. Chronic c-AUCB treatment significantly decreased systolic blood pressure (SBP) (133 ± 1 vs. 163 ± 3 mmHg) and increased sodium excretion (1.23 ± 0.10 vs. 0.59 ± 0.03 mmol/day) in 2K1C rats. HET-0016 did not affect SBP and sodium excretion. In acute experiments, renal blood flow (RBF) was decreased in 2K1C rats (5.0 ± 0.2 vs. 6.9 ± 0.2 ml·min(-1)·g(-1)). c-AUCB normalized RBF in 2K1C rats (6.5 ± 0.6 ml·min(-1)·g(-1)). HET-0016 also increased RBF in 2K1C rats (5.8 ± 0.2 ml·min(-1)·g(-1)). Although RBF and glomerular filtration rate (GFR) remained stable in normotensive rats during renal arterial pressure (RAP) reductions, both were significantly reduced at 100 mmHg RAP in 2K1C rats. c-AUCB did not improve autoregulation but increased RBF at all RAPs and shifted the pressure-natriuresis curve to the left. HET-0016-treated 2K1C rats exhibited impaired autoregulation of RBF and GFR. Our data indicate that c-AUCB displays antihypertensive properties in 2K1C hypertension that are mediated by an improvement of RBF and pressure natriuresis. While HET-0016 enhanced RBF, its anti-natriuretic effect likely prevented it from producing a blood pressure-lowering effect in the 2K1C model.

In the present study, we examined the effects of soluble epoxide hydrolase (sEH) inhibition on the development of angiotensin II-dependent hypertension and on renal function in transgenic rats with inducible expression of the mouse renin gene (strain name Cyp1a1-Ren-2). Hypertension was induced in these rats by indole-3-carbinol (I3C; 0.3% in the diet) for 12 days. The sEH inhibitor cis-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (c-AUCB) was given in two doses (13 or 26 mg l-1) in drinking water. Blood pressure (BP), body weight (BW) and renal excretory parameters were monitored in conscious animals during the experiment. Renal haemodynamics was assessed at the end of treatment in anaesthetized rats. I3C administration resulted in severe hypertension with a rise in systolic BP from 118 ± 2 to 202 ± 3 mmHg, a loss of BW from 266 ± 5 to 228 ± 4 g and a rise in proteinuria from 14 ± 2 to 34 ± 3 mg day-1. Both doses of c-AUCB significantly attenuated the development of hypertension (systolic BP of 181 ± 4 and 176 ± 4 mmHg, respectively), the loss in BW (256 ± 4 and 259 ± 3 g, respectively) and the degree of proteinuria (27 ± 2 and 25 ± 3 mg day-1, respectively) to a similar extent. Moreover, c-AUCB prevented the reduction in renal plasma flow (5.4 ± 0.4 vs. 4.6 ± 0.3 ml min-1 g-1) and significantly increased sodium excretion (0.84 ± 0.16 vs. 0.38 ± 0.08 μmol min-1 g-1) during I3C administration. These data suggest that the oral administration of c-AUCB displays antihypertensive effects in Ren-2 transgenic rats with inducible malignant hypertension via an improvement of renal function.

Objective: The contribution of epoxyeicosatrienoic acids (EETs) and 20-hydroxyeicosatetraenoic acid (20-HETE) as cytochrome P-450 metabolites of arachidonic acid in the regulation of the nonclipped kidney function in two-kidney, one-clip (2K1C) Goldblatt hypertensive rats was investigated during the phases of initial and stable hypertension, that is, 7 or 27 days after clipping, respectively., Methods: Male Hannover Sprague-Dawley rats had the right renal artery clipped or underwent sham operation. Urinary excretion of EETs, their inactive metabolites dihydroxyeicosatrienoic acids and of 20-HETE was measured. Intrarenal cytochrome P-450 protein expression and the activities of epoxygenase, omega-hydroxylase and soluble epoxide hydrolase were also determined. The responses of renal hemodynamics and electrolyte excretion of the nonclipped kidney to left renal artery infusions of inhibitors of EETs or 20-HETE formation (MS-PPOH and DDMS, respectively) were measured., Results: In 2K1C rats, urinary excretion of EETs was significantly lower and that of 20-HETE was higher than that in sham-operated animals only on day 27 after clipping. Intrarenal inhibition of EETs significantly decreased renal hemodynamics and sodium excretion in sham-operated but not in 2K1C rats. Intrarenal inhibition of 20-HETE decreased sodium excretion in sham-operated rats but elicited increases in renal hemodynamics and sodium excretion in 2K1C rats., Conclusion: Our results indicate that the nonclipped kidney of Goldblatt 2K1C rats in the phase of sustained hypertension exhibits decreased intrarenal EETs and elevated 20-HETE levels as compared with the kidney of sham-operated animals. This suggests that altered production and action of cytochrome P-450-derived metabolites during this stable phase contributes to the mechanism of Goldblatt 2K1C hypertension.

Objective: We evaluated the effects of salt restriction and of increasing dietary salt loading on blood pressure and the renin-angiotensin system in transgenic rats with inducible hypertension., Methods: Hypertension was induced in Cyp1a1-Ren-2 rats through dietary administration of the natural xenobiotic indole-3-carbinol (0.3%), which activates the renin gene. Rats were fed either a normal-salt diet (0.6% NaCl), three different high-salt diets (2, 4 and 8% NaCl) or a low-salt diet (<0.04% NaCl). Blood pressure was monitored by radiotelemetry. Angiotensin II (ANG II) levels were determined by radioimmunoassay., Results: Induction of the renin gene by administration of indole-3-carbinol resulted in normal-salt diet fed animals in the development of severe hypertension that was accompanied by marked increases in plasma and kidney ANG II levels. Feeding the low-salt diet substantially attenuated the development of hypertension. Treatment with the 2 and 4% high-salt diet did not worsen the course of hypertension and did not alter ANG II levels when compared with rats on the normal salt diet. Feeding the 8% high-salt diet exacerbated the course of hypertension and was associated with further strong increases in plasma and kidney ANG II levels., Conclusion: Our results demonstrate that after induction of the renin gene in Cyp1a1-Ren-2 transgenic rats inappropriate increases in plasma and kidney ANG II levels in response to very high dietary salt intake are responsible for the development of severe hypertension in this model of inducible renin transgenic rats.

The relationship between angiotensin II (ANG II) and endothelin-1 (ET-1) is known to be complex; both peptides can initiate and potentiate the gene expression of each other. This pilot study investigated the effects of the AT(1) receptor blocker losartan or the direct renin inhibitor aliskiren on mean arterial pressure (MAP) and albuminuria and the renal ANG II and ET-1 levels. 3-month-old male Ren-2 transgenic rats (TGR) were treated either with losartan (5 mg kg(-1) day(-1)) or aliskiren (10 mg kg(-1) day(-1)) for 10 weeks. At the end of the experiment, rats were decapitated and cortical and papillary parts of kidneys were separated. Plasma and tissue ANG II levels were measured by RIA and tissue ET-1 concentrations by ELISA. In all four groups of animals ET-1 levels were lowest in renal cortex and more than 100-fold higher in the papilla. Cortical and papillary ET-1 concentrations in untreated TGR significantly exceeded those of control HanSD rats and were significantly depressed by both drugs. In both strains, papillary ANG II concentrations were moderately but significantly higher than cortical ANG II, TGR exhibited higher ANG II levels both in cortex and papilla as compared to control HanSD rats. Aliskiren and losartan at the doses used depressed similarly the levels of ANG II in cortex and papilla and reduced ET-1 significantly in the renal cortex and papilla below control levels in HanSD rats. Albuminuria, which was more than twice as high in TGR as in HanSD rats, was normalized with aliskiren and reduced by 28% with losartan, although MAP was reduced to a similar degree by both drugs. Despite similar reductions of MAP and renal ET-1 and ANG II levels aliskiren appears to be more effective than losartan, at the doses used, in reducing albuminuria in heterozygous hypertensive Ren-2 rats.

The aim of this study was first to evaluate the effects of persistent or transient blockade of the angiotensin II (ANG II) receptor AT(1) on the development of hypertension and end-organ damage in hypertensive Ren-2 transgenic rats (TGR), and second to assess the potential role of AT(2) receptors in the control of blood pressure (BP) in this monogenetic model of hypertension. Male heterozygous TGR and Hannover Sprague-Dawley (HanSD) rats fed a normal salt diet were treated from day 32 of age either persistently until the end of the experiment (day 100 of age) or transiently until day 56 of age with the selective AT(1) receptor antagonist candesartan or with the combination of candesartan and the AT(2) receptor antagonist PD 123319. Persistent treatment with candesartan completely prevented the rise in BP, proteinuria and the increase in left ventricular weight/body weight ratio, whereas transient treatment with candesartan was effective only as long as the drug was administered. In the presence of candesartan, PD 123319 was without effect. Our results show that in male heterozygous TGR persistent candesartan treatment completely prevented hypertension and end-organ damage as long as the drug was administered, whereas transient AT(1 )receptor blockade had no long-term effects., (Copyright 2007 S. Karger AG, Basel.)

Background: The present study was performed in hypertensive Ren-2 transgenic rats (TGR) and in normotensive Hannover Sprague-Dawley (HanSD) rats. First, the intrarenal protein expression of CYP4A, the enzyme catalyzing the formation of 20-hydroxyeicosatetraenoic acid (20-HETE), and of CYP2C23, the enzyme responsible for epoxyeicosatrienoic acid (EET) production, was evaluated. Second, the renal functional responses to inhibition of the intrarenal formation of 20-HETE and EETs were investigated., Methods: Renal hemodynamics and electrolyte excretion were evaluated in response to the administration of inhibitors of 20-HETE and EET formation into the renal artery. In renal cortical tissue, CYP4A and CYP2C23 protein expression was assessed by Western blot analysis. Urinary concentrations of 20-HETE and EETs were measured using a fluorescent HPLC assay., Results: TGR have higher kidney CYP4A protein expression and urinary 20-HETE excretion but significantly lower CYP2C23 protein expression and urinary EET excretion than HanSD. Intrarenal inhibition of 20-HETE and EET formation decreased sodium excretion in HanSD, whereas inhibition of 20-HETE increased urinary excretion of sodium in TGR without altering renal hemodynamics., Conclusions: Our data suggest that in TGR, deficient intrarenal synthesis of EETs combined with increased synthesis of 20-HETE with its stimulation of tubular sodium absorption may contribute to the development of hypertension in TGR., (2007 S. Karger AG, Basel)

Objective: Since there is as yet no general agreement regarding the role of plasma and kidney angiotensin II (ANG II) in the development of hypertension in Ren-2 transgenic rats (TGR), in the present study we evaluated plasma and kidney ANG II levels in anesthetized and conscious TGR and in normotensive Hannover-Sprague-Dawley rats (HanSD) fed a normal salt diet (NS). Given the importance of ANG II in the development of salt-sensitive hypertension, and the fact that hypertensinogenic actions of ANG II are mediated via ANG II type 1 (AT1) receptors, the effects of high salt (HS) intake and of sodium depletion on blood pressure (BP), ANG II levels and kidney AT1 receptor protein expression in TGR and HanSD were also examined., Methods: Rats were maintained on a NS diet (0.6% NaCl) or fed a HS diet (2% NaCl) for 4 days or were sodium depleted (40 mg/l furosemide for 1 day followed by 3 days of 0.01% NaCl diet). They were sacrificed either by an overdose of anesthetic (thiopental sodium) or by decapitation (without anesthetic) and plasma and kidney ANG II levels were determined by radioimmunoassay during the prehypertensive (32 days old), the early (52 days) and the maintenance (90 days) phases of hypertension. Total kidney AT1 receptor protein levels were assessed by Western blot analysis., Results: In anesthetized animals fed the NS diet, plasma ANG II levels were lower in 32-day-old TGR than in HanSD, but at 52 and 90 days of age no significant differences were noted. ANG II concentrations in kidney tissue were similar in 32- and 90-day-old TGR and HanSD, but were higher in 52-day-old TGR than in HanSD. In contrast, in conscious animals immediately after decapitation, plasma and kidney ANG II levels were higher in TGR than in HanSD at all ages. HS diet did not change BP but suppressed ANG II levels in HanSD at all ages. In contrast, HS diet increased BP but did not decrease plasma and kidney ANG II levels in TGR at all ages. Sodium restriction did not alter BP and resulted in a marked increase in ANG II levels in HanSD, but caused a significant decrease in BP in TGR without altering plasma or tissue ANG II concentrations. There were no significant differences in renal AT1 receptor protein expression between HanSD and TGR at any age of any of the experimental groups., Conclusions: On the basis of our present results we conclude that TGR exhibit a disrupted interaction between sodium homeostasis and the regulation of the renin-angiotensin system (RAS) activity which results in the loss of BP regulation in this model.

Background: Previous studies have implicated that normotensive rats with normal renal renin activity respond to anesthesia and surgery with greater increases in plasma and kidney angiotensin II (ANG II) concentrations than ANG II-dependent hypertensive rats with intrarenal renin depletion. In the present study, we therefore compared plasma and kidney ANG II levels in anesthetized and conscious normotensive and ANG II-dependent hypertensive rats., Methods: Salt-replete Hannover-Sprague-Dawley rats (HanSD) served as controls. As models of ANG II-dependent hypertension we used: 1st, transgenic rats harboring the Ren-2 renin gene (TGR); 2nd, two-kidney, one-clip (2K1C) Goldblatt hypertensive rats, and, 3rd, ANG II-infused hypertensive rats. As additional model with enhanced renin-angiotensin system (RAS) activity, salt-depleted HanSD and TGR were employed., Results: In anesthetized salt-repleted HanSD, plasma and kidney ANG II levels were higher than in salt-repleted TGR, ANG II-infused and 2K1C rats. Salt depletion caused marked increases in ANG II levels in HanSD but did not alter them in TGR. In contrast, in conscious animals immediately after decapitation plasma and kidney ANG II levels were similar in salt-repleted and salt-depleted TGR, in ANG II-infused rats, in the clipped kidney of 2K1C rats and in salt-depleted HanSD and in all these groups they were significantly higher than in salt-repleted HanSD., Conclusions: These findings indicate that anesthesia increases plasma and kidney ANG II levels in HanSD to a greater degree than in ANG II-dependent models of hypertension. Therefore, the results from studies employing anesthetized animals must be interpreted with caution., (Copyright 2006 S. Karger AG, Basel.)

Background and Methods: We investigated kidney function, renal endothelin-1 concentration, prepro-endothelin-1 mRNA as well as endothelin receptor A and B mRNA expression and receptor properties in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) with intact renal nerves and 7 days after renal denervation. In addition, responses of renal function to the non-selective ETA/ETB receptor blocker bosentan (10 mg/kg i.v. bolus injection) were studied., Results: In SHR, renal papillary prepro-endothelin-1 mRNA expression, endothelin-1 tissue concentrations and endothelin receptor density were significantly lower than in normotensive rats. Renal denervation was associated with a decrease in papillary tissue prepro-endothelin-1 mRNA and in WKY rats also with a significant reduction in papillary endothelin-1 content without affecting ET receptor density. Bosentan did not alter renal blood flow or glomerular filtration rate but decreased urine flow rate in both intact normotensive and hypertensive rats, whereas it decreased urine sodium and potassium excretion only in intact WKY. Bosentan had no effects on renal function in renal denervated rats., Conclusion: Since renal papillary endothelin-1 appears to counteract the fluid and sodium retaining effects of renal nerve activity, an impaired renal endothelin-1 synthesis in SHR may contribute to excessive sodium retention and thus to the pathogenesis of hypertension in SHR., (Copyright 2006 S. Karger AG, Basel.)

Aim: The role of the kidney endothelin system in the renal regulation of fluid and electrolyte excretion was investigated in Wistar-Kyoto (WKY) and Long-Evans (LE) rats in which we found previously marked differences in the renal excretory responses to endothelin A receptor blockade., Methods: The selective endothelin A and B receptor antagonists BQ-123 (16.4 nmol kg(-1) min(-1)) and BQ-788 (25 nmol kg(-1) min(-1)) were infused i.v. for 50 min in conscious chronically instrumented WKY and LE rats and their renal function and renal endothelin system were studied., Results: Without effects on glomerular filtration rate or renal blood flow, BQ-123 and BQ-788 decreased by more than 50% (P < 0.01) both urine flow rate and electrolyte excretion in WKY rats but only urine flow rate (P < 0.05) in LE rats. Endothelin-1 content, preproET-1/GPDH mRNA ratio, B(max) and K(d) of total endothelin receptors in renal cortex did not differ between the two strains. In contrast, plasma endothelin-1 concentration (0.58 +/- 0.04 vs. 1.05 +/- 0.01 femtomol mL(-1); P < 0.01), renal papillary ET-1 concentration (68 +/- 5 vs. 478 +/- 62 fmol mg(-1) protein; P < 0.01) and preproET-1/GPDH mRNA ratio (0.65 +/- 0.09 vs. 0.88 +/- 0.05; P < 0.05) as well as total endothelin receptor number in renal papilla (B(max) 5.3 +/- 0.4 vs. and 9.0 +/- 1.2 pmol mg(-1) protein; P < 0.05) were markedly lower in LE than in WKY rats. In vitro studies showed that in both strains ET(B) receptors on renal cortical membranes amounted between 65% and 67% and on papillary membranes between 85% and 88%., Conclusion: The present data show that the selective ET(A) or ET(B) receptor blockade differentially affects tubular water and salt handling, which becomes apparent in conditions of low renal papillary endothelin receptor number and tissue endothelin-1 concentration.

Objective: We investigated the responses of mean arterial pressure and renal blood flow to intravenous and intrarenal angiotensin II, plasma and kidney angiotensin II concentrations and renal angiotensin receptor subtype 1 protein expression, and renal functional responses to intravenous and intrarenal angiotensin receptor 1 blockade with candesartan., Methods: In male anaesthetized transgenic rats and Hannover Sprague-Dawley rats aged 36-38 days mean arterial pressure and renal blood flow were determined after intravenous and intrarenal boluses of angiotensin II. Mean arterial pressure, renal blood flow and sodium excretion after intravenous or intrarenal candesartan were studied. Plasma and kidney angiotensin II concentrations were determined by radioimmunoassay. Renal angiotensin receptor subtype 1 protein levels were analysed by immunoblotting., Results: The responses of mean arterial pressure and renal blood flow to angiotensin II were significantly greater in transgenic than in Hannover Sprague-Dawley rats. The administration of candesartan resulted in comparable decreases in mean arterial pressure and increases in renal blood flow and sodium excretion in both groups of rats. Renal angiotensin receptor subtype 1 protein levels were no different between Hannover Sprague-Dawley and transgenic rats., Conclusions: Plasma and kidney angiotensin II levels were lower in anaesthetized transgenic rats but, in contrast, were higher in decapitated transgenic rats when compared with Hannover Sprague-Dawley rats, suggesting that the kidney function of prehypertensive transgenic rats is under inappropriately high angiotensin II-dependent influence.

Background: Increasing evidence suggests that angiotensin-(1-7) [Ang-(1-7)] acts as an endogenous antagonist of Ang II when the renin-angiotensin system (RAS) is activated. In the present study, we therefore compared the effects of acute intrarenal (i.r.) Ang-(1-7) receptor blockade on renal function under conditions of normal and increased intrarenal Ang II concentration., Methods: Salt-replete Hannover-Sprague Dawley rats (HanSD) served as control animals. As models with enhanced action of Ang II we first used transgenic rats harboring the Ren-2 renin gene (TGR), second, Ang II-infused rats, third, 2-kidney, 1-clip (2K1C) hypertensive rats on normal salt intake, and fourth, salt-depleted TGR and HanSD., Results: I.r. Ang-(1-7) receptor blockade elicited significant decreases in glomerular filtration rate (GFR), renal plasma flow (RPF), and sodium excretion in 2K1C rats, and in salt-depleted TGR and HanSD. In contrast, i.r. Ang-(1-7) receptor blockade did not significantly change GFR, RPF, and sodium excretion in salt-replete TGR and HanSD, or in Ang II-infused rats., Conclusion: These findings suggest that under conditions of normal intrarenal RAS activity and increased intrarenal Ang II action by infusion of Ang II or by insertion of a renin gene in salt-replete conditions, Ang-(1-7) is not an important factor in the regulation of renal function. In contrast, under conditions of endogenous RAS activation due to clipping of the renal artery or to sodium restriction, Ang-(1-7) serves as opponent of the vasoconstrictor actions of Ang II.

Aims: The present study was performed to evaluate the role of nitric oxide (NO) and its interaction with superoxide anion (O2-) in the regulation of blood pressure (BP) and renal function during the developmental phase of hypertension in Ren-2 transgenic rats (TGR). The first aim was to compare BP and renal functional responses to acute NO synthase (NOS) inhibition achieved by intravenous (i.v.) infusion of Nomega-nitro-L-arginine-methyl ester (L-NAME) in prehypertensive heterozygous TGR and in transgene-negative Hannover Sprague-Dawley (HanSD) rats. The second aim was to evaluate whether scavenging of O2- by infusion of the superoxide dismutase mimetic tempol increases NO bioavailability which therefore should augment BP and renal functional responses to L-NAME., Methods: Rats were anesthetized, prepared for clearance experiments and BP and renal functional responses were evaluated in response to i.v. L-NAME administration (20 microg.100 g(-1).min(-1)) without or with tempol pretreatment (i.v., 300 microg.100 g(-1).min(-1)). In renal cortical tissue, nitrotyrosine protein expression was assessed by immunoblotting as marker of O2- production and urinary 8-epi-PGF(2alpha) excretion as marker of intrarenal oxidative stress was assessed by enzyme immunoassay., Results: BP, glomerular filtration rate (GFR), renal plasma flow (RPF) and sodium excretion were similar in TGR and HanSD. L-NAME infusion induced greater increases in BP in TGR than in HanSD (+42 +/- 4 vs. +25 +/- 3 mmHg, p < 0.05). In the absence of a significant change in GFR, L-NAME caused similar decreases in RPF (-32 +/- 6 and -25 +/- 4%, p < 0.05) in TGR and HanSD. Despite significantly higher renocortical expression of nitrotyrosine and urinary 8-epi-PGF2alpha excretion in TGR than in HanSD, pretreatment with tempol did not augment the rise in BP and the decrease in RPF induced by L-NAME., Conclusions: The greater BP response to L-NAME in TGR suggests that prehypertensive TGR exhibit an enhanced NO activity in the systemic vasculature as compared with HanSD. Despite increased intrarenal oxidative stress in TGR, the dependency of the intrarenal vascular tone on NO appears to be similar in TGR and HanSD. The lack of a compensatory increase in renal NO activity may partially account for the enhanced renal vascular response to ANG II present in TGR.

The present study was performed to evaluate the role of neuronal nitric oxide synthase (nNOS)-derived nitric oxide (NO) during the developmental phase of hypertension in transgenic rats harboring the mouse Ren-2 renin gene (TGR). The first aim of the present study was to examine nNOS mRNA expression in the renal cortex and to assess the renal functional responses to intrarenal nNOS inhibition by S-methyl-L-thiocitrulline (L-SMTC) in heterozygous TGR and in age-matched transgene-negative Hannover Sprague-Dawley rats (HanSD). The second aim was to evaluate the role of the renal sympathetic nerves in mediating the renal functional responses to intrarenal nNOS inhibition. Thus, we also evaluated the effects of intrarenal L-SMTC administration in acutely denervated TGR and HanSD. Expression of nNOS mRNA in the renal cortex was significantly increased in TGR compared with HanSD. Intrarenal administration of L-SMTC decreased the glomerular filtration rate (GFR), renal plasma flow (RPF) and sodium excretion and increased renal vascular resistance (RVR) in HanSD. In contrast, intrarenal inhibition of nNOS by L-SMTC did not alter GFR, RPF or RVR and elicited a marked increase in sodium excretion in TGR. This effect of intrarenal L-SMTC was not observed in acutely denervated TGR. These results suggest that during the developmental phase of hypertension TGR exhibit an impaired renal vascular responsiveness to nNOS derived NO or an impaired ability to release NO by nNOS despite enhanced expression of nNOS mRNA in the renal cortex. In addition, the data indicate that nNOS-derived NO increases tubular sodium reabsorption in TGR and that the renal nerves play an important modulatory role in this process.

In the present study we investigated the possible role of angiotensin-(1-7) [Ang-(1-7)] in modulating renal functional responses to intrarenal (i.e.) infusion of angiotensin II (ANG II) in normotensive anesthetized rats. ANG II (6 ng/min, n = 14) decreased glomerular filtration rate (GFR), renal plasma flow (RPF), absolute and fractional sodium excretion by -24 +/- 5, -25 +/- 6, -44 +/- 6 and -28 +/- 7%, respectively (p < 0.05). i.r. infusion of Ang-(1-7) (50 ng/min, n = 13) did not significantly alter GFR (+6 +/- 4%) but reduced RPF by -19 +/- 7% (p < 0.05). Ang-(1-7) increased absolute and fractional sodium excretion by +36 +/- 6 and +37 +/- 8%, respectively (p < 0.05). Infusion of Ang-(1-7) did not prevent the decreases in GFR and RPF but completely blunted the decreases in absolute (-2 +/- 2%) and fractional sodium excretion (-4 +/- 4%) induced by ANG II (n = 11). Blockade of the Ang-(1-7) receptor by [7-D-Ala]-Ang-(1-7) (5 microg/min, n = 11) significantly decreased GFR, RPF, absolute and fractional sodium excretion by -28 +/- 7, -20 +/- 5, -32 +/- 7 and -24 +/- 4%, respectively (p < 0.05), suggesting that the action of endogenous ANG II is unopposed by compensatory effect of endogenous Ang-(1-7). i.r. infusion of Ang-(1-7) (n = 10) did not alter the effect of Ang-(1-7) receptor blockade on RPF (-21 +/- 6%) but blunted its effects on GFR (+4 +/- 3%) and absolute (+7 +/- 5%) and fractional (+6 +/- 4%) urinary sodium excretion probably by displacing the receptor blocker. While exogenous ANG II during blockade of the Ang-(1-7) receptor and the AT(2) receptor (by PD 123319; 1 microg/min i.r., n = 9) resulted in the same decreases in absolute and fractional sodium excretion (-39 +/- 8 and -38 +/- 6%, respectively, p < 0.05) as did ANG II in the absence of Ang-(1-7) receptor blockade. These results suggest that in normotensive rats high i.r. Ang-(1-7) concentration attenuates the tubular, i.e. sodium reabsorptive effect, but not the vascular effect of exogenous i.r. ANG II. Results obtained during blockade of Ang-(1-7) and of AT(2) receptors imply that AT(2) receptors play a role in tubular sodium reabsorption in the presence of high ANG II concentration., (Copyright 2002 S. Karger AG, Basel)

Background/aims: It has been shown that nitric oxide (NO) generated from neuronal NO synthase (nNOS) counteracts angiotensin II mediated vasoconstriction in the pre- and in the postglomerular microcirculation. Previous studies have demonstrated that the nNOS expression in the macula densa of the renal cortex is enhanced by dietary salt restriction. In view of the well-known fact that dietary salt restriction also leads to an activation of the renin-angiotensin system, the present study was performed to assess the role of nNOS-derived NO in the regulation of the renal function in rats maintained on control (C) and low-salt (LS) diets., Methods: Groups of rats were fed either the C or the LS diet. On day 13 after adaptation to the appropriate diet, renal clearance studies were performed to determine the effects of acute nNOS inhibition either by S-methyl-L-thiocitrulline (L-SMTC) or by N(omega)-propyl-L-arginine (L-NPA) on renal hemodynamics and sodium excretory function. In separate groups of rats maintained on either the C or the LS diet, the mRNA levels of nNOS and of renin in the renal cortex were examined using the semiquantitative reverse-transcriptase polymerase chain reaction., Results: Intrarenal infusion of vehicle (0.9% saline; 4 microl/min) did not change glomerular filtration rate (GFR), renal plasma flow (RPF), or sodium excretion in either C diet or LS diet rats. Acute intrarenal infusion of L-SMTC (0.3 mg/h) and L-NPA (0.01 mg/h) decreased GFR (-14 +/- 5 vs. -13 +/- 3%), RPF (-19 +/- 6 vs. -17 +/- 5%), and sodium excretion (-17 +/- 5 vs. -16 +/- 4%) in C diet rats as compared with control values (p < 0.05). In contrast, in LS rats, intrarenal administration of either L-SMTC or L-NPA did not cause significant changes in GFR, RPF, and sodium excretion. Furthermore, the mRNA expression for nNOS in the renal cortex was moderately increased in LS rats as compared with C rats (densitometric ratios of nNOS mRNA/GAPDH mRNA 0.31 +/- 0.01 vs. 0.22 +/- 0.04, p < 0.05), in parallel with the renin expression (renin mRNA/GAPDH mRNA ratios 1.4 +/- 0.2 vs. 1.0 +/- 0.1, p < 0.05)., Conclusions: These results indicate that in normotensive rats kept on a normal salt intake nNOS-derived NO modulates both afferent and efferent arteriolar tones. In contrast, rats on an LS diet exhibit an impaired renal vascular responsiveness to nNOS-derived NO or an impaired ability to release NO by nNOS despite enhanced expression of nNOS mRNA in the renal cortex. In addition, the lack of effect of acute nNOS inhibition on renal function suggests that NO derived by nNOS does not participate in counteracting the vasoconstrictor influences of elevated circulating and/or intrarenal angiotensin II levels on pre- and postglomerular microcirculation in rats on an LS diet., (Copyright 2002 S. Karger AG, Basel)

Renal excretory function and hemodynamics are determined by the effective circulating plasma volume as well as by the interplay of systemic and local vasoconstrictors and vasodilators. Microgravity results in a headward shift of body fluid. Because the control conditions of astronauts were poorly defined in many studies, controversial results have been obtained regarding diuresis and natriuresis as well as renal hemodynamic changes in response to increased central blood volume, especially during the initial phase of space flight. Renal excretory function and renal hemodynamics in microgravity are affected in a complex fashion, because during the initial phase of space flight, variable mechanisms become operative to modulate the effects of increased central blood volume. They include interactions between vasodilators (dopamine, atrial natriuretic peptide, and prostaglandins) and vasoconstrictors (sympathetic nervous system and the renin-angiotensin system). The available data suggest a moderate rise in glomerular filtration rate during the first 2 days after launch without a significant increase in effective renal plasma flow. In contrast, too few data regarding the effects of space flight on renal function during the first 12 hours after launch are available and are, in addition, partly contradictory. Thus, detailed and well-controlled studies are required to shed more light on the role of the various factors besides microgravity that determine systemic and renal hemodynamics and renal excretory function during the different stages of space flight.

Results from space have been unexpected and not predictable from the results of ground-based simulations. Therefore, the concept of how weightlessness and gravity modulates the regulation of body fluids must be revised and a new simulation model developed. The main questions to ask in the future are the following: Does weightlessness induce a diuresis and natriuresis during the initial hours of space flight leading to an extracellular and intravascular fluid volume deficit? Can sodium in excess be stored in a hitherto unknown way, particularly during space flight? Why are fluid and sodium retaining systems activated by spaceflight? Why are the renal responses to saline and water stimuli in space attenuated compared with those of ground simulations? How can the effects of weightlessness on fluid and electrolyte regulation be correctly simulated on the ground? The information obtained from space may be of relevance to fluid and electrolyte balance in edematous patients.

Angiotensin-(1-7), (Ang-(1-7)), a metabolite of Ang II and /or Ang I, was infused into the renal artery (i.r.a) of anesthetized dogs in order to demonstrate its possible direct renal action. The dose administered, 15 Ig/kg BW/min in isotonic saline (0.072 ml/kg BW/min) throughout the experiment, did not influence the systemic arterial pressure and water and sodium excretion from the contralateral noninfused kidney. Renal blood flow (RBF) was measured by an electromagnetic flowmeter, glomerular filtration rate (GFR) by (exogenous) creatinine clearance. In other groups of animals, either EXP 3174, an AT-1 receptor antagonist alone (30 Ig/kg BW/ min) or together with Ang-(1-7) (15 Ig/kg BW/min), were infused. In the last group, the AT-2 receptor antagonist PD 123319, 10 Ig/kg BW/min, was added to the infusion of Ang-(1-7). A small but significant decrease of RBF from 4.51+/-0.32 to 3.8+/-0.29 ml/g BW/min occurred after Ang-(1-7); this decrease was very similar when PD 123319 was added. However, an increase to 4.98+/-0.34 ml/g BW/min was seen after the addition of EXP 3174 to the i.r.a. infusion of Ang-(1-7); this increase was similar to the increase observed after EXP 3174 alone (5.21+/-0.33; p<0.02 in both cases). A very small but significant increase in GFR was seen after Ang-(1-7) + EXP 3174 or after the AT-1 blocker alone (0.64+/-0.049 and 0.62+/-0.05 vs. 0.6+/-0.05 ml/g BW/min in the Time Control Group, p<0.01 and 0.05, respectively). Water, sodium and urea excretion rates were increased in all groups infused with Ang-(1-7); after the combination of Ang-(1-7) + EXP 3174, all increases were higher than after every substance alone; however, statistical significance (p<0.05) was reached in sodium excretion values only. Potassium excretion rates were increased just in those groups in which EXP 3174 was present in the infusion fluid. In summary, Ang-(1-7) i.r.a. infusion in the dog is followed by increases in water, sodium and urea (but not potassium) excretion rates, highly probably of tubular origin. This effect is not completely blocked by the AT-1 - and not at all by the AT-2 receptor antagonist - thus indirectly suggesting another receptor could play a role. A small decrease in RBF disappears after EXP 3174, thus indicating an AT-1 receptor action.

1. Obstructive jaundice predisposes the kidney to acute renal failure. Endothelin (ET), a potent renal vasoconstrictor and modulator of the tubular action of arginine vasopressin, has been suggested to play a pathogenetic role in acute renal failure. In the present study we therefore investigated renal function and the renal ET system in rats on day 4 after bile-duct ligation (BDL) or sham-operation (SO), without (n = 7 in each group) and with treatment with bosentan, a combined ETA/ETB receptor blocker, (n = 5 in each group). 2. On day 4 after BDL, serum bilirubin had increased to 226 +/- 10 mumol/l (SEM) as compared with 6 +/- 2 mumol/l in SO rats. Endogenous creatinine clearance, an index of glomerular filtration rate, was significantly reduced to 0.7 +/0 0.1 ml min-1 g-1 of kidney weight after BDL as compared with 1.1 +/- 0.1 ml min-1 g-1 of kidney weight after SO (P < 0.05). Bosentan prevented the decrease in glomerular filtration rate (1.0 +/- 0.2 ml min-1 g-1 of kidney weight), as well as polyuria and defective concentrating ability, in BDL rats. 3. Plasma ET concentration on day 4 after surgery (28.2 +/- 1.5 pmol/l) was higher (P < 0.01) in BDL than in SO rats (12.9 +/- 1.5 pmol/l) and rose further in bosentan-treated BDL and SO rats (43.4 +/- 5.1 compared with 21.9 +/- 6.6 pmol/l). Urinary ET excretion was significantly higher in BDL rats than in SO rats (1.58 +/- 0.22 compared with 1.28 +/- 0.18 pmol 24 h-1 100 g-1 of body weight; P < 0.05). 4. ET synthesis by glomeruli isolated from BDL rats was lower [81 +/- 19 fmol h-1 (mg of protein)-1] than that from SO-rats [139 +/- 28 fmol h-1 (mg of protein)-1; P < 0.05], whereas papillary ET synthesis was higher in BDL [10 +/- 3 fmol h-1 (mg of protein)-1] than in SO rats [4 +/- 1 fmol h-1 (mg of protein)-1; P < 0.05]. 5. The results indicate that BDL is associated with increased plasma ET concentration and suppression of GFR. Enhanced renal inner medullary collecting-duct ET synthesis, which is reflected by increased urinary ET excretion, may reduce distal tubular water absorption in BDL rats. Increased circulating and renal papillary ET synthesis may thus contribute to renal dysfunction and predispose the kidney to acute renal failure in obstructive jaundice.

Patients with intra- or extrahepatic bile-duct obstruction are susceptible to acute renal failure (ARF) especially when undergoing major surgery. We observed in jaundiced rats 4 days after bile-duct ligation (BDL) a decrease in GFR accompanied by polyuria which is associated with increased urinary thromboxane (TX) excretion and glomerular TXB2 synthesis. The TXA2/ PGH2 receptor antagonist daltroban normalized GFR but not urine concentration. There was also a rise in plasma and urinary endothelin (ET-1) with increased papillary ET synthesis. The ETA/ETB receptor blocker bosentan restored GFR and the renal concentrating ability. Since we showed previously that ET-induced decreases in renal perfusion and ultrafiltration coefficient Kf are mediated by other autacoids such as TX, this may explain why both bosentan and daltroban normalized GFR. These results suggest that increased renal glomerular TX and vascular and inner medullary collecting duct ET synthesis contribute to defective GFR and distal tubular function in experimental BDL. Similar alterations may also predispose the human kidney to ARF in patients with obstructive jaundice.

1. Unilateral left renal artery occlusion for 1 h in a group of 8 untreated female Sprague-Dawley rats resulted in oliguric acute renal failure (ARF) persisting for more than 6 h after reflow, i.e. after reperfusion of the kidney by removal of the arterial clamp. In a second group of 8 rats with left unilateral ARF the effects of levemopamil (L), a calcium entry blocker with 5-hydroxytryptamine2 (5-HT2) receptor antagonistic properties, were studied. Rats received L as a continuous infusion (6 mg kg-1 h-1) from 1 h before ischaemia until 6 h after reflow. 2. Endogenous creatinine clearance, an estimate of glomerular filtration rate (GFR), of left ischaemic kidneys of untreated rats was almost completely abolished and urine flow was 0.05 +/- 0.02 and 0.03 +/- 0.01 ml h-1 100 g-1 body weight (body wt.) at 2 and at 6 h of reflow, respectively. In contrast, left ischaemic kidneys of L-treated rats revealed significantly higher GFR (0.10 +/- 0.02 and 0.03 +/- 0.01 ml min-1 g-1 kidney weight (k.wt.); P < 0.01) and urine flow (0.51 +/- 0.05 and 0.15 +/- 0.04 ml h-1 100 g-1 body wt.; P < 0.05) at 2 and 6 h of reflow, respectively. 3. At 6 h of reflow, mitochondria from the cortex of left ischaemic kidneys of untreated rats showed significantly reduced ATP synthesis when compared to right intact kidneys (0.06 +/- 0.02 vs 0.26 +/- 0.02 mumol ATP mg-1 protein min-1 (P < 0.01)). In contrast, in L-treated rats, ATP synthesis of left ischaemic kidneys was largely preserved (0.17 +/- 0.01 mumol ATP mg-1 protein min-1). 4. Ischaemia of left kidneys resulted in a significant decrease in medullary Na-K-ATPase activity to 9.6 +/- 2.4 as compared to 20.4 +/- 3.7 mumol P(i) h-1 mg-1 protein in the intact right kidneys which was not prevented by L (9.4 +/- 2.4 mumol P(i) h-1 mg-1 protein). 5. In untreated rats the calcium content in cortical mitochondria from left ischaemic kidneys had risen 2 fold to 23.0 +/- 1.8 at 6 h of reflow as compared to 12.2 +/- 0.3 nmol mg-1 protein in right intact kidneys (P < 0.01). This rise in mitochondrial calcium was not significantly attenuated by treatment with L (19.9 +/- 1.7 nmol mg-1 protein). 6. The results show that L transiently converted oliguria into non-oliguria during the early phase after reflow in ischaemic ARF, i.e. after reperfusion following 1 h of complete interruption of renal perfusion. The present data suggest indirectly that the 5-HT2-antagonistic properties of L rather than its calcium channel blocking action maintains GFR at low level and protects mitochondrial function early after reflow in this model of ischaemic ARF.

1. Patients with obstructive jaundice are especially susceptible to acute renal failure. We have previously observed that in rats with bile duct ligation impaired renal function is associated with increased urinary thromboxane excretion. 2. In the present study we therefore investigated, in rats with bile duct ligation, renal function, urinary thromboxane excretion and thromboxane B2 synthesis by isolated glomeruli as well as the effects of the thromboxane A2/prostaglandin H2 receptor antagonist Daltroban on renal function in rats with bile duct ligation as compared with sham-operated rats. 3. On the fourth day after bile duct ligation (n = 7 rats) endogenous creatinine clearance as an estimate of glomerular filtration rate was significantly reduced to 0.74 +/- 0.05 (SEM) as compared with 1.06 +/- 0.09 ml min-1 g-1 kidney weight in sham-operated rats (n = 7, P < 0.01). In rats with bile duct ligation, urine volume was slightly increased, whereas urinary sodium (Na+) (P < 0.001) and potassium (K+) (P < 0.01) excretion as well as urine osmolarity (P < 0.05) were significantly reduced and lower than in sham-operated rats. 4. Urinary thromboxane excretion was significantly higher in rats with bile duct ligation than in sham-operated rats: 116.6 +/- 22.3 versus 56.8 +/- 10.2 pmol 24 h-1 100 g-1 body weight (P < 0.05). Thromboxane B2 synthesis in glomeruli isolated from rats with bile duct ligation was also significantly higher than in sham-operated rats: 12.6 +/- 2.0 versus 6.4 +/- 0.9 pmol h-1 mg-1 protein (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

It was previously shown in man that metoclopramide (MCP), a dopamine (DA)-2 receptor blocker, attenuates the natriuresis of water immersion. In the present study, we therefore investigated the effects of MCP on renal function and atrial natriuretic peptide (ANP) release in conscious rats. Under basal conditions MCP did not affect glomerular filtration rate (GFR) (7.4 +/- 1.7 ml/min/kg without and 7.8 +/- 0.6 ml/min/kg with MCP), urinary fractional excretion of Na (FENa) (0.3 +/- 0.1% without and 0.3 +/- 0.1% with MCP) and K (FEK) (20.6 +/- 1.4% without and 28.0 +/- 6.2% with MCP) or plasma ANP (37 +/- 5 pmol/l without and 31 +/- 6 pmol/l with MCP). During acute saline loading equal to a 10% rise in body weight, which significantly (p < 0.05) increased GFR, MCP again had no effects on GFR (8.8 +/- 1.8 ml/min/kg with vs. 9.7 +/- 2.5 ml/min/kg without MCP), FENa (24.5 +/- 6.9% with vs. 20.4 +/- 5.1% without MCP), FEK (52.5 +/- 6.9% with vs. 52.5 +/- 9.5% without MCP) and plasma ANP (89 +/- 8 pmol/l with vs. 91 +/- 9 pmol/l without MCP). These results indicate that DA does not modulate renal function or ANP release via DA-2 receptors under basal conditions nor in response to acute saline loading in conscious rats.

To investigate the potential pathogenetic and therapeutic roles of thromboxane A2 (TXA2) and its receptor blockade, respectively, in the early phase of ischemic acute renal failure (ARF), renal function, TXB2 excretion, and the effects of the specific TXA2 receptor antagonist sulotroban (SU) in a model of unilateral renal artery occlusion in conscious female Sprague-Dawley rats were studied. Occlusion of the left renal artery for 1 h in untreated (i.e., vehicle-treated) rats (N = 8) resulted in oliguric ARF. In SU-treated rats (N = 8), the drug was given as an i.v. bolus of 5 mg/kg body wt, followed by a continuous infusion of 0.5 mg/min.kg body wt from 1 h before and during ischemia and for 6 h after reflow. After 1 h of ischemia, urine volume of left ischemic kidneys from untreated rats had decreased from 13.2 +/- 2.8 to 1.0 +/- 0.3 and 0.5 +/- 0.2 microL/min.100 g at 2 and 6 h of reflow, respectively, and GFR had decreased from 0.32 +/- 0.04 mL/min.100 g body wt to undetectable values. At 6 h of reflow, medullary Na-K-ATPase was slightly (P < 0.05) reduced in left ischemic kidneys, whereas medullary and papillary enzyme activities were compensatorily increased (P < 0.01) in right intact kidneys. The ADP/O ratio of cortical mitochondria was 41% (P < 0.05) and ATP synthesis was 77% (P < 0.01) lower than in right intact kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)

1. 125I-labelled c-atrial natriuretic peptide-(4-23) was used as radioligand for the direct quantification of atrial natriuretic peptide clearance receptors, and 125I-labelled rat atrial natriuretic peptide-(1-28) was used for the determination of total and biologically active atrial natriuretic peptide receptors, in renal glomerular and papillary membrane preparations of chronically salt-loaded and control rats. 2. The membrane preparation technique included acid-washing (pH 5), and receptor binding was assessed by saturation studies at 4 degrees C for 3 h. Chronic salt loading revealed a 35% decrease in clearance receptor number in the glomerular membrane and a 42% decrease in the papillary membranes. The absolute decrease in clearance receptor number was almost identical with the observed reduction in absolute number of total atrial natriuretic peptide receptors. Biologically active receptors were not affected by chronic salt loading. 3. Selective downregulation of clearance receptors for atrial natriuretic peptide may reflect an important role for the rat renal atrial natriuretic peptide system in long-term fluid and electrolyte regulation.

In six patients with essential hypertension (EH) and in six healthy volunteers (C) the effects of a 60-min intravenous (iv) infusion of human atrial natriuretic peptide (alpha-hANP) (24 ng/min/kg) on systemic and renal hemodynamics and renal excretory function were evaluated. Basal plasma ANP concentrations in patients with EH were higher (P less than .05) than in C (30.9 +/- 4.5 v14.0 +/- 1.7 pmol/L). Maximal effects of alpha-hANP infusion occurred after 30 to 60 min. Blood pressure (BP) declined from 154 +/- 5/109 +/- 4 to 139 +/- 7/94 +/- 4 in EH and from 117 +/- 1/72 +/- 2 to 106 +/- 1/65 +/- 3 mm Hg in C (P less than .05). Cardiac output (CO) increased transiently from 6.1 +/- 0.3 to 6.5 +/- 0.4 L/min in EH and from 6.8 +/- 0.3 to 7.2 +/- 0.5 L/min in C, whereas heart rate (HR) remained constant both in patients with EH and in C (69 +/- 3 to 72 +/- 5 and 60 +/- 3 to 63 +/- 3/min). The increases in urine flow and in urinary sodium excretion from 3.6 +/- 0.2 to 16.0 +/- 2.0 mL/min and from 230 +/- 33 to 1004 +/- 137 mumol/min, respectively, in EH were more pronounced than in C (from 3.9 +/- 1.0 to 8.4 +/- 0.8 mL/min and from 211 +/- 37 to 451 +/- 84 mumol/min); (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Infusion of substance P into the renal artery was previously shown to cause a significant natriuresis which was associated with increased kallikrein excretion. Since the renal kinin and prostaglandin (PG) systems may be interrelated, the present study was performed to investigate the effects of substance P on renal function and its potential interaction with the renal PG system in the conscious rat. 24 female Sprague-Dawley rats were infused intravenously with substance P (1 ng . min-1 . kg-1 body weight) and the body weight was kept constant by an intravenous infusion of 0.45% saline. Substance P had no effects on arterial blood pressure, glomerular filtration rate (GFR) and 125I-hippuran clearance in the absence or presence of indomethacin (INDO). Basal UPGE2 V was unaltered by substance P infusion but was suppressed by INDO before and during substance P by 80 and 88%, respectively. Substance P raised urinary flow rate (V) by 105%, CH2O by 96%, UNaV by 378%, UKV by 48% and UPO4V by 147% (p less than 0.001). Although INDO significantly suppressed V, CH2O, and UNaV during all collection periods, it did not affect absolute UPO4V and UKV and the relative rise in V, CH2O, and UNaV induced by substance P. Thus, the diuretic and natriuretic effects of substance P are not mediated by renal PG, but are partially blunted by INDO through increased distal absorption of sodium and water, INDO has no effect on substance P-induced alterations in proximal tubular function.

1. In six healthy volunteer subjects polydipsic water loading significantly increased urine volume from 1203 +/- 242 (SEM) to 5072 +/- 320 ml/24 h (P less than 0.001) with a significant decrease in urinary osmolality. This increase in urine volume by more than fourfold was associated with a slight increase in urinary excretion of prostaglandin E2 from 466 +/- 66 to 1017 +/- 174 pmol/24 h (P = 0.05). 2. In five patients with central diabetes insipidus mean urine volume of 10 838 +/- 107 ml/24 h was reduced to 1205 +/- 204 ml/24 h (P less than 0.001) by treatment with 1-desamino-8-arginine vasopressin (desamino-[Arg8]vasopressin; 15 microgram/day) with a significant rise in urinary osmolality. Desamino-[Arg8]vasopressin treatment was associated with a significant increase of suppressed urinary excretion of prostaglandin E2 (PGE2) in four of these patients from 246 +/- 66 to 2643 +/- 677 pmol/24 h (P less than 0.01). 3. Concomitant treatment with indomethacin in addition to desamino-[Arg8]vasopressin significantly suppressed urinary excretion of PGE2 and significantly increased urinary osmolality as compared with treatment with desamino-[Arg8]vasopressin alone. 4. Desamino-[Arg8]vasopressin significantly increased urinary excretion of adenosine 3':5'-cyclic monophosphate (cyclic AMP). However, there was no further change in urinary excretion of cyclic AMP during concomitant indomethacin treatment. 5. The results suggest that urine flow itself is not an important determinant of urinary PGE2 excretion. In patients with central diabetes insipidus the urinary concentrating response to desamino-[Arg8]vasopressin is enhanced during inhibition of prostaglandin synthesis without changes in urinary excretion of cyclic AMP.

1. Aprotinin, a potent kallikrein inhibitor, was given to conscious rats with and without expansion of the extracellular fluid volume with isotonic saline. 2. In non-expanded rats aprotinin had no effect on arterial pressure, glomerular filtration rate (GFR), hippuran clearance, urinary flow rate, absolute sodium and potassium excretion or free-water clearance. 3. In volume-expanded rats aprotinin significantly reduced GFR, hippuran clearance, urine volume (V) UNaV, UKV and Cwater/GFR without effect on systemic arterial pressure. 4. Urinary immunoreactive prostaglandin E2 excretion significantly increased during the expansion phase but returned to below the control range during stable extracellular fluid volume expansion. 5. Aprotinin significantly suppressed urinary immunoreactive prostaglandin E2 excretion in non-expanded rats and in volume-expand rats during the expansion phase, but not during stable expansion. 6. The results suggest that the kallikrein-kinin system may contribute to changes in renal function during extracellular volume expansion. This action may not necessarily be associated with changes in renal prostaglandin E2 activity.

In 38 conscious rats divided into seven groups, acute unilateral ischemic renal failure was induced by 1 hour of complete occlusion of the left renal artery while the contralateral kidney remained intact. Renal excretory function of the left kidney was monitored up to 144 hours after ischemia and revealed a typical course of oliguric renal failure with oligoanuria persisting for more than 48 hours. Urinary osmolality and sodium concentration became plasma isotonic after release of renal artery occlusion and approximated control values on day 6 after ischemia. In nine rats, the i.v. infusion of furosemide before (6 microgram/min/100 g body wt) and after (12 microgram/min/100 g body wt) renal artery occlusion protected the ischemic kidney from oligoanuria with endogenous creatinine clearance of 0.42 +/- 0.11 ml/min/g kidney wt 5 hours after ischemia. Tubular absorption of sodium and water was at least partially preserved 36 hours after ischemia when infusion of furosemide was stopped. The loop diuretic significantly (P less than 0.01) increased total urinary prostaglandin (PG) E2 excretion before and after renal artery occlusion; and 5 hours after ischemia, PGE2 excretion from the ischemic kidney significantly exceeded that from the intact kidney (P less than 0.05). Indomethacin (1 mg/100 g body wt) administered in six animals markedly suppressed control PGE2 excretion (P less than 0.05) as well as the furosemide-induced rise in urinary PG excretion before and after ischemia but did not modify the protective effect of the diuretic in this experimental model. Inhibition of PG synthesis, however, reduced urinary flow rate and sodium and potassium excretion of the contralateral intact kidney and almost completely prevented its compensatory rise in creatinine clearance. The results indicate that mechanisms other than the intrarenal prostaglandin system must be considered to mediate the protective effects of furosemide in acute ischemic renal failure.

Neither a temporary increase in salt intake nor the activation of endogenous vasoconstrictor hormones alone will cause a rise in blood pressure in healthy subjects. High blood pressure rather results from an augmented product of cardiac output and peripheral vascular resistance, which also requires defective baroreceptor function. Experimental and clinical evidence from renal transplantation suggests that high blood pressure may be transmitted by the kidney. Morphological or functional inability of the kidney to adequately eliminate excessive salt, as in renoparenchymal hypertension, or with enhanced renal adrenergic activity in the presence of high salt intake, may induce initially salt- and volume-dependent hypertension with increased cardiac output and normal peripheral vascular resistance. In the case of reduced nephron population, this first stage was shown to be followed by a normalization of cardiac output, but a simultaneous rise in peripheral vascular resistance, including decreased compliance of the venous capacitance vessels. What are the underlying mechanisms which convert volume-dependent hypertension into high resistance hypertension without necessarily reducing central blood volume? Increased central blood volume, which may stimulate the secretion of an endogenous Na-K-ATPase inhibitor or other endogenous factors, may cause decreased transmembranous sodium transport, resulting in elevated intracellular concentrations of sodium and calcium with enhanced responsiveness of the vascular smooth muscle cell to vasoconstrictor hormones. Since increased central blood volume also decreases baroreceptor sensitivity, the disturbed interplay of cardiac output and peripheral vascular resistance will result in high blood pressure.

1. The effects of jaundice on renal and circulatory function were investigated in chronic bile duct ligated (CBDL) rats 6 days after surgery. Sham operated (SO) animals served as controls. 2. Body weight was significantly reduced, whereas blood pressure remained unaltered, 6 days after bile duct ligation when serum bilirubin had risen to 169 +/- 18 (SEM) as compared with 2.8 +/- 0.3 mumol/l in SO rats. When compared with control values before surgery, urinary volume had significantly increased and absolute excretion of sodium, potassium, chloride and phosphate had decreased on day 6 after CBDL. Endogenous creatinine clearance was markedly depressed when compared with SO rats. Whereas fractional excretion of potassium remained unaltered, fractional excretion of sodium and of phosphate was significantly increased. 3. Except for a significant increase in urinary thromboxane B2 (TXB2) excretion in CBDL rats, no significant changes were observed in urinary excretion of prostaglandin (PG) E2, in the synthesis of PGE2, 6-keto-PGF1 alpha and TXB2 by isolated aortic tissue in vitro, nor in renal and cardiac adenosine triphosphatase activities or renal cortical mitochondrial function. 4. The adenosine triphosphate content of kidney cortex and cardiac mitochondrial function were significantly depressed in CBDL rats. 5. The results demonstrate that jaundice in CBDL rats is associated with functional and metabolic disturbances of the kidney and cardiac muscle, which may contribute to the renal and haemodynamic characteristics observed in jaundiced animals and humans.

We have previously shown that a natriuretic factor which is present in a small molecular weight fraction (IV) of serum and urine from salt loaded animals and healthy subjects, respectively, inhibits the Na-K-ATPase enzyme in vitro and also binds to a specific digoxin antibody. In the present study digoxin-like immunoreacting activity (DLIA) was therefore determined in the serum of healthy volunteers during low (35 nmol/day) and high (greater than 400 mmol/day) sodium intake and of patients with chronic renal failure and serum creatinine concentrations ranging from 127 to 757 mumol/l. DLIA was determined with a radioimmunoassay for digoxin in native serum and in the salt (III) and post-salt (IV) serum fractions eluted from a Sephadex G-25 column. DLIA in native serum of healthy subjects was less than 0.125 ng/ml. After gel filtration DLIA eluted exclusively in the small molecular weight salt (F III) and post-salt (F IV) fractions. Whereas DLIA increased in F III and decreased in F IV, total DLIA in F III + IV slightly increased from 0.37 +/- 0.03 to 0.49 +/- 0.05 ng/ml (p less than 0.01) with the change from low to high sodium intake. DLIA in native serum of uremic patients ranged from 0 to 1.70 ng/ml and was detectable consistently only in patients with serum creatinine concentrations above 250 mumol/l. DLIA in F III which averaged 0.22 +/- 0.04 ng/ml and total activity which ranged from 0.11 to 0.88 ng/ml closely correlated with the degree of renal impairment (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)