Renin Activity Concentration Research Articles

P4560The efficacy and safety of mineralocorticoid-receptor antagonists: spironolactone and eplerenone in resistant hypertension and chronic kidney disease stages 3

Abstract Chronic kidney disease (CKD) is the most frequent comorbidity associated with resistant hypertension (RH). Despite mineralocorticoid-receptor antagonists (MRAs) have been proven to be effective in RH, this drugs are underused in this patients and must be used very carefully in CKD due to the higher risk of hyperkalemia (HK) and significant renal dysfunction (RD), particularly in combination with renin angiotensin inhibitors. The aim was to compare the efficacy and safety of using of MRAs: spironolactone (SP) and eplerenone (EP) in RH and CKD stages 3 and determine predictors of developing HK and worsening of renal function (RF). Methods 54patients with true RH (antihypertensive treatment mean of 3.4±1.4 drugs per patient including diuretic, ACE-I or an ARB) and CKD 3 (baseline eGFR between 30 and 60 ml/min) were included in the study. The potassium (K) and creatinine (C) levels, plasma aldosterone (AS) and active renin concentration (ARC) were estimated at baseline. After chemical evaluation, 28 patients started on SP treatment with a mid-dose 18 mg daily (titrated), 26 patients started on EP with a mid-dose 24 mg (titrated). K and RF were checked at weeks 1, 4, 8, 12. At baseline and after 12 weeks of therapy, patients underwent clinic and 24-hour BP measurement. Results SP and EP both effectively decreased BP (9.5/-3.7 mm Hg; P<0.05 for both; 9.9±3.9 mm Hg; P<0.05 for both; respectively), changes in BP were dose dependent and not significantly different. K and C levels increased significantly after the start of MRAs treatment for both SP and EP patients: mean of K on SP increased from 4.26±0.61 to 5.25±0.69 mEq/l and on EP from 4.29±0.71 to 5.13±0.71 mEq/l (P<0.001; P<0.001; respectively) and was dose dependent. After 12 weeks of treatment the incidence of sever HK (K ≥6.0 mmol/L) was <4% (two on SP 25 mg and two on EP 25 mg). A K 5.5–5.9 mmol/L occurred in 9 patients (four on SP) and was predicted by baseline K ≥5.0 mmol/L, eGFR ≤40 ml/min/1.73m2 and dose of diuretic. Mean of eGFR on SP decreased from 45.26±3.19 to 40.15±2.88 ml/min/1.73m2 and on EP from 46.29±3.56 to 39.13±2.99 ml/min/1.73m2 (P<0.001; P<0.001; respectively). Three patients (one on SP) experienced significant RD result in withdrew MRAs. Two cases of gynecomastia were reported with SP use resulting in a switch to EP. Female, ARC >20 ng/ml and eGFR≤40 ml/min/1.73m2 at baseline had modest discriminative powers for predicting decline RF (P<0.05; P<0.01; P<0.001; respectively). Conclusion SP and EP demonstrated comparable efficacy in RH and CKD 3, but EP was well tolerated. In both groups MRAs treatment resulted in a significant dose dependent rise in K and C levels. Female, higher levels of ARC and eGFR were identified as potential predictors of worsening of RF. The occurrence of HK was predicted by baseline K level and eGFR. So, caution should be advised when using MRAs in RH with CKD 3 and an ARC >20 ng/ml, P of ≥5.0 mmol/L and eGFR ≤40 ml/min/1.73m2 for safety reasons.

Abstract P2031: Control Of Antihypertensive Effect Of Small Interfering RNA Targeting Angiotensinogen

A single dose of small interfering ribonucleic acids (siRNA) targeting angiotensinogen (AGT) provides a strong and sustained antihypertensive effect, lasting weeks to months in preclinical models. It is not known whether conventional vasopressors are effective to reverse RNAi-mediated blood pressure lowering. Here, we investigated whether conventional vasopressors can elevate arterial pressure under conditions of AGT depletion. Spontaneously hypertensive rats on a low-salt diet (<0.03% NaCl) were treated for 4 weeks with siRNA (10 mg/kg fortnightly; s.c.), supplemented with fludrocortisone (6 mg/kg/day; s.c.), midodrine (4 mg/kg/day; s.c.) or a high-salt diet (4% NaCl) during the final 2 weeks (all groups n=6-7). Before and after 2 weeks of siRNA, blood pressure responses to intravenous bolus injections of angiotensin II (0.05; 0.5 and 5 μg/kg) and noradrenalin (0.1; 1.0 and 10 μg/kg) were examined in anesthetized rats, via radiotelemetry. Baseline mean arterial pressure (MAP; 136±3 mmHg) was lowered by 19±1 mmHg by AGT siRNA combined with a low-salt diet. Acute pressor responses to angiotensin II and noradrenalin were identical before and after siRNA. Fludrocortisone restored MAP to baseline levels (137±3 mmHg), as did replacing the low-salt diet with a high-salt diet (139±4 mmHg). Midodrine had no effect. Under low salt conditions, siRNA virtually abolished plasma AGT by 99.2±0.1% to 6±1 nM, and increased active plasma renin concentrations. AGT was not altered by midodrine, only marginally increased by high sodium intake, but increased to 20±5% of pre-siRNA treatment levels by fludrocortisone, paralleled by near-elimination of plasma renin levels by 97.6±0.9% to 2.1±0.9 ng angiotensin I/mL.h. Collectively, these data indicate that the efficacy of angiotensin II and noradrenaline to raise blood pressure is not affected by RNAi-mediated AGT suppression. Increased sodium intake or fludrocortisone may represent chronic, less invasive alternatives for controlling blood pressure during AGT depletion, of which the latter seems to be facilitated by amplification of AGT production.

THE EFFECT OF SPIRONOLACTONE VERSUS TORSEMIDE ON BLOOD PRESSURE TARGETS IN RESISTANT HYPERTENSION PATIENTS

Objective: to evaluate effects on blood pressure (BP) control in two treatment options spironolactone (SPIR) versus torsemide (TOR) as an add-on therapy in resistant hypertensive (RAH) patients. Design and method: We studied 78 patients with true RAH confirmed by the office and ambulatory BP monitoring (ABPM). Patients were randomized into 2 groups through 12 weeks of once daily treatment with of SPIR (25–50 mg) or TOR (5–10 mg) in addition to their baseline triple-combination and then rotated with drugs. BP was measured in the office and by ABPM. Changes in laboratory tests were also studied. The predictive values of plasma aldosterone, active renin concentration (ARC) and aldosterone-renin ratio (ARR), serum potassium, 24-h urinary excretion sodium of determining the antihypertensive response were analyzed. Results: There were no significant differences on the reduction of average office BP and average nighttime BP by SPIR and TOR. SPIR reduced average systolic 24-h BP by 11.7 mmHg and average systolic daytime BP by 12.2 mmHg compared with a reduction of 8.9 mmHg (P < 0.05) and 9.1 mmHg (P < 0.05) with TOR, respectively. Overall, 36.8 % RAH patients achieved targets of clinical BP and 24-h ABPM levels on SPIR and 30.9 % on TOR. After 12 weeks of treatment mean plasma potassium concentrations increased from 4.3 to 4.7 mmol/L (P < 0.0001) on SPIR but did not significant change on TOR. Serum potassium (β = −0.441, P < 0.05), 24-h urinary excretion sodium (β = 0.432, P < 0.05) and ARR (β = 0.543, P < 0.03) were predictors of BP-lowering effect of SPIR and plasma aldosterone (β = −0.680, P < 0.001), ARC (β = 0.463, P < 0.03) were predictors of reduction BP for TOR in multivariate modeling. Conclusions: Greater antihypertensive effect of SPIR is related to aldosterone status, urinary sodium excretion and serum potassium level in resistant hypertension. TOR may be suited for RAH patients that have high ARC and in people with lower sodium intake or high serum potassium level.

The state of renin-aldosterone system in patients with resistant arterial hypertension

Purpose. The understanding of pathophysiology and clinical characteristics of resistant hypertension (RH) remains elusive. The aim of this work was to study the relationships between clinical course of RH and levels of renin and aldosterone (AS). Materials and methods. A total of 47 patients with true RH were included in the study. The control group included 50 patients with controlled arterial hypertension (CAH). All patients underwent general clinical examination, calculation of body mass index (BMI), office blood pressure measurement, determination of plasma potassium, AS and active renin concentrations (ARC), assessment of plasma aldosterone-to-renin ratio, urinary albumin excretion, albumin-creatinine ratio (ACR), uric acid, serum creatinine, calculation of glomerular filtration rate (GFR) by Cockcroft–Gault formula, echocardiography. Results. AS and ARC levels were significantly higher (AS 145.21 ± 11.90 ng/ml and 122.04 ± 8.60 ng/ml, P < 0.001; ARC 18.21 ± 3.50 ng/ml and 14.40 ± 2.20 ng/ml, P < 0.05) in patients with RH compared to those with CAH, respectively. At the same time, among patients with RH, only 38 % had a normal ARC; increased ARC was in 27 % and reduced ARC was in 35 % of patients. Among patients with CAH, 78 % had a normal ARC; increased ARC was in 7 % and reduced ARC was in 15 % of patients. In patients with CAH, there was negative correlation between AS and ARC levels (r = -0.38, P < 0.05), at the same time in patients with RH, no correlation was found between AS and ARC levels. However, in patients with RH, there were negative correlations between AS, ARC and GFR (r = -0.36, P < 0.05; r = -0.32, P < 0.05, respectively); positive – ARC and left ventricular mass index (r = 0.43, P < 0.05); AS and ACR (r = 0.76, Р < 0.01); AS and left ventricular end-diastolic volume (r = 0.38, P < 0.05). Moreover, significant correlations were found between ARC and BMI (r = 0.59, P < 0.001), AS and BMI (r = 0.42, P < 0.05). Conclusions. The results indicate that in patients with RH, higher renin and AS levels are mediated by overweight as well as renin and AS have a different influence on target organs in RH. Furthermore, stimulation of AS production occurs regardless of the renin-angiotensin system and angiotensin II effects. The group of patients with RH is not homogeneous according to renin concentration and “low-renin” and “high-renin” hypertension are more frequently registered among them. It seems that pathophysiologic mechanisms are different in each case and need to be identified for the selection of antihypertensive agents to treat patients successfully.

SUN-365 Characteristics of Primary Aldosteronism without Suppression of Plasma Renin Activity

Introduction: Primary aldosteronism (PA) is a common cause of secondary hypertension. It is characterized by excess production of aldosterone from the adrenal glands resulting in suppressed plasma renin activity (PRA) by a negative feedback regulation. Thus, if a patient with hypertension had an unsuppressed PRA, the possibility of PA might be excluded. However, we have observed some PA patients with unsuppressed PRA in our hospital. Here, we report clinical characters of PA patients with unsuppressed PRA. Methods: We searched for PA patients with unsuppressed PRA (Escaped PRA group) from 969 patients who underwent segmental adrenal venous sampling (S-ATS) in our hospital between April 2009 and March 2018. Escaped PRA group were those with PRA level of >1.0 ng/mL/hr in any two or more blood samples obtained in resting position, and had aldosterone producing adenomas (APAs) in which CYP11B2 expression was confirmed histopathologically. We also enrolled patients with APAs with suppressed PRA as a control group (34 females, 35 females ). All patients in the control group had PRA level of < 1.0 ng/mL/hr in any two or more blood samples obtained in resting position and had macroadenomas in which CYP11B2 expression was confirmed. We compared clinical characteristics between Escaped PRA group and Control group. Results: We found that 7 cases (3 males, 4 females) were in the Escaped PRA group (PRA; 2.3±0.8 ng/mL/hr). One of them showed a gap between PRA and Active Renin Concentration (ARC). Compared to the control group (PRA; 0.3±0.2 ng/mL/hr), the escaped PRA group had no significant difference in body mass Index, blood pressure, urinary aldosterone, and serum potassium. The escaped PRA group tended to be younger compared to control group (53.0±4.4 years-old vs 47.4±10.8 years-old, P = 0.12) and have decreased eGFR Escaped (74.4±20.0 mL/min/1.73 m2 vs 86.3±19.3 mL/min/1.73 m2, P = 0.088). Only serum cortisol level after 1 mg dexamethasone suppression test showed a significant difference (Escaped PRA group; 1.9±0.5 mg/dL, Control group 1.4±3.0 mg/dL, P = 0.011). Conclusion: Excess cortisol has been reported to increase PRA through increasing renin substrate and suppressing ACTH-dependent aldosterone secretion. We should not exclude the possibility of PA in patients without suppressed plasma renin activity, especially who had a cortisol excess.

Responses of the renin-angiotensin-aldosterone system in pregnant chronic kidney disease patients with and without superimposed pre-eclampsia.

BackgroundWomen with chronic kidney disease (CKD) are at increased risk of superimposed pre-eclampsia (SPE). Accurate identification of SPE is challenging. We hypothesized that specific components of the renin–angiotensin–aldosterone system (RAAS) would discriminate between CKD and SPE. The aim of the study was to establish differences in circulating and intrarenal RAAS in women with CKD with and without SPE and compare these to normotensive controls (NCs) and women with pre-eclampsia (PE).MethodsWhite European NC women (n = 20), women with PE (n = 9), normotensive CKD without SPE (n = 8) and with SPE (n = 11) were recruited in the third trimester. Plasma renin, plasma and urine total angiotensinogen (AGT) concentrations were quantified by enzyme-linked immunosorbent assay, urinary tetrahydroaldosterone (TH-aldo) concentration by gas chromatography-mass spectrometry and placental growth factor (PlGF) by immunoassay.ResultsUrinary TH-aldo:creatinine ratios were lower in women with PE or SPE compared with NC or women with CKD (P < 0.05 for all). The same group differences were observed for plasma active renin and PlGF concentrations (P < 0.05 for all). Urine total AGT was higher in women with PE compared with NC (P < 0.05) and urine TH-aldo:urine AGT was lower (P < 0.05). However, women with SPE had lower urinary AGT concentrations compared with women with PE (P < 0.05). No differences in plasma total AGT were observed between groups.ConclusionsWomen with SPE have a lower urinary TH-aldo:creatinine ratio, lower plasma active renin and lower PlGF concentrations than women with CKD, comparable to women with PE without pre-existing disease, suggestive of similar pathophysiology. These data suggest disruption of the RAAS pathway in SPE similar to PE. Exploration of the predictive value of RAAS components for adverse pregnancy events in women with CKD is required.

Effects of mineralocorticoid and AT-1 receptor antagonism on the aldosterone-renin ratio (ARR) in primary aldosteronism patients (EMIRA Study): rationale and design.

Current guidelines recommend withdrawal of treatments that affect the aldosterone/renin ratio (ARR) when screening for primary aldosteronism (PA). However, abandonment of mineralocorticoid-receptor antagonist (MRA) and/or blockers of the renin-angiotensin system can deteriorate control of blood pressure (BP) and hypokalemia. Thus, in consecutive patients with an unambiguous diagnosis of PA in washout from confounding treatments and subtyped by AVS, we will compare within-patient plasma aldosterone and active renin concentration, and the ARR values, measured at baseline, and after a 1-month treatment with MRA alone and combined with an AT-1 receptor blocker (ARB). Patients on a regular salt intake will be treated with canrenone (50-100 mg orally) for 1 month, after which olmesartan (10 or 20 mg orally) will be added for another month with up-titration of both treatments over the first 2 weeks to control BP and hypokalemia, while background therapy will be maintained. The biochemical variables and the ARR will be assessed in an identical manner at baseline values and after each month of treatment. With a sample size of 40 patients, the study will have a 95% power to show a clinically significant 20% change in the ARR at a 5% α value using a two-sided paired t test. Hence, this study will allow us to determine if an MRA alone, or added to an ARB at doses that control BP and hypokalemia, affects or not the ARR, thus allowing to establish if these agents can be administered or must be forbidden during the screening of PA.

Impact of obesity on the association of active renin and plasma aldosterone concentrations, and aldosterone-to-renin ratio with preeclampsia.

To evaluate the association of active renin concentration (ARC), plasma aldosterone concentration (PAC) and aldosterone-to-renin ratio (ARR) with the risk of preeclampsia (PE), in particular according to the status of obesity. This retrospective case-control study involved 90 women with PE (mean gestation 35.6 ± 3.6 weeks) and 90 age-matched control women with uncomplicated pregnancies (mean gestation 38.5 ± 2.5 weeks). ARC and PAC were measured by radioimmunoassay; ARR calculated as PAC to ARC ratio. PE cases were stratified into 5 percentiles groups, and analyzed in multivariate logistic regression. Women with PE had significantly lower median ARC and PAC than control women, which were confirmed by percentiles analysis. Spearman correlation demonstrated negative correlation of ARC with body mass index, systolic/diastolic blood pressure. PAC correlated negatively with systolic/diastolic blood pressure, but positively with baby weight, ARC and ARR. On the other hand, ARR positively correlated with BMI and PAC, but negatively with ARC. Lower PAC was associated with PE, irrespective of body weight, while ARC levels were significantly lower in non-obese PE cases vs. control women. ARR was not significantly different between PE cases and control women, when stratified according to obesity. Low ARC and PAC in third trimester are more strongly associated with preeclampsia respectively in non-obese and obese women.

Cure With Cryoablation of Arterial Hypertension Due to a Renin-Producing Tumor

We herein report on a 20 years old woman with stage I hypertension, who was found to carry a renin-producing tumor (RPT). Due to her young age, the patient underwent screening measurement of plasma renin and aldosterone, abdominal computed tomography (CT) angiography, and selective renal vein renin assessment to identify secondary hypertension. The patient was screened for secondary causes of hypertension and was diagnosed with secondary aldosteronism. Therefore, she underwent an abdominal computed tomography (CT) angiography that was reported as unremarkable. Selective renal vein renin studies showed overproduction of renin in the right kidney and a re-evaluation of her CT allowed detection of an 8-mm mass in her right kidney, suggesting the presence of a RPT. Considering the technical difficulty of renal sparing surgery a CT-guided cryoablation was undertaken, which provided long-term cure of arterial hypertension and normalization of plasma active renin concentration. RPTs usually present with a clinical phenotype featuring stage III and/or malignant hypertension and are held to be exceptionally rare. This case is unique in that it presented with stage I hypertension and a mild clinical phenotype. Moreover, to our knowledge this is the first case of RPTs shown to be safely treated with CT-guided cryoablation and found to be cured at long-term.

Low- and High-renin Heart Failure Phenotypes with Clinical Implications.

Blockade of the renin-angiotensin system (RAS) represents a main strategy in the therapy of heart failure with reduced ejection fraction (HFrEF), but the role of active renin concentration (ARC) for guiding therapy in the presence of an RAS blockade remains to be established. This study assessed angiotensin profiles of HFrEF patients with distinct RAS activations as reflected by ARC. Two cohorts of stable chronic HFrEF patients on optimal medical treatment (OMT) were enrolled. We assessed ARC and all known circulating angiotensin metabolites, including AngI and AngII, by mass spectrometry to investigate the effect of different therapy modalities. Low- and high-renin HFrEF patients were identified by ARC screening and subsequently characterized by their angiotensin profiles. Although different modes of RAS blockade resulted in typical AngII/AngI ratios, concentrations of (AngI+AngII) strongly correlated with ARC [r = 0.95, P < 0.001] independent of therapy mode. Despite RAS blocker treatment with angiotensin-converting enzyme inhibitors (ACE-I) or angiotensin II type 1 receptor blockers (ARB), which anticipated ARC upregulation, about 30% of patients showed lower/normal range ARC values. ARC did not correlate with N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations and New York Heart Association (NYHA) stages. Angiotensin concentrations were profoundly diminished for the low-ARC group compared with the high-ARC group: AngI [6.4 ng/L (IQR: 2.1-12.5) vs 537.9 ng/L (IQR: 423.1-728.4), P < 0.001 for ACE-I; and 4.5 ng/L (IQR: 1.4-11.2) vs 203.0 ng/L (IQR: 130.2-247.9), P = 0.003 for ARB] and AngII [<1.4 ng/L (IQR: <1.4-1.5) vs 6.1 ng/L (IQR: 2.0-11.1), P = 0.002 for ACE-I and 4.7 ng/L (IQR: <1.4-12.3) vs 206.4 ng/L (IQR: 142.2-234.4), P < 0.001 for ARB]. In addition to NT-proBNP and NYHA stages, ARC enables classification of HFrEF patients receiving OMT into more distinguished neurohumoral HFrEF phenotypes, offering a rationale for adaptive therapeutic interventions.

Macrolides for KCNJ5–mutated aldosterone-producing adenoma (MAPA): design of a study for personalized diagnosis of primary aldosteronism

Purpose: Aldosterone-producing adenoma (APA) is the main curable cause of endocrine hypertension cause of primary aldosteronism (PA) and it is in up to 66% of all cases investigated with adrenal vein sampling (AVS). Mutations in the KCNJ5 potassium channel involve up to 70% of APA and cause the most florid PA phenotypes. The recent finding that macrolide antibiotics specifically inhibit in vitro the altered function of mutated KCNJ5 channels has opened new horizons for the diagnosis and treatment of APA with KCNJ5 mutations in that it can allow identification and target treatment of PA patients harbouring a mutated APA. Thus, we aimed at investigating if clarithromycin and roxithromycin, two macrolides that potently blunt mutated Kir3.4 channel function in vitro, affect plasma aldosterone concentration in adrenal vein blood during AVS and in peripheral blood, respectively, in PA patients with a mutated APA.Methods and design: We designed two proof of concept studies. In study A: consecutive patients with an unambiguous biochemical evidence of PA will be exposed to a single dose of 250 mg clarithromycin during AVS, to assess its effect on the relative aldosterone secretion index in adrenal vein blood from the gland with and without APA. In study B: consecutive hypertensive patients submitted to the work-up for hypertension will receive a single oral dose of 150 mg roxithromycin. The experimental endpoints will be the change induced by roxithromycin of plasma aldosterone concentration and other steroids, direct active renin concentration, serum K+, systolic and diastolic blood pressure.Discussion: We expect to prove that: (i) clarithromycin allows identification of mutated APA before adrenalectomy and sequencing of tumour DNA; (ii) the acute changes of plasma aldosterone concentration, direct active renin concentration, and blood pressure in peripheral venous blood after roxithromycin can be a proxy for the presence of an APA with somatic mutations.

PP.23.04] RESPONSES OF THE RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM TO PLASMA VOLUME DEPLETION IN PRE-ECLAMPSIA &amp; SUPERIMPOSED PRE-ECLAMPSIA

Objective: Women with chronic kidney disease (CKD) are at increased risk of superimposed pre-eclampsia (SPE) and associated adverse pregnancy outcomes. Diagnosis of SPE using blood pressure and proteinuria is of limited use because these may develop in women with CKD even without the condition. Inaccurate diagnosis may result in unnecessary iatrogenic preterm delivery. Plasma and urinary aldosterone concentrations are elevated in patients with CKD, but suppressed in established pre-eclampsia (PE). The aim of the study was to determine plasma active renin, total plasma and urinary angiotensinogen (AGT) and aldosterone availability in women with CKD with and without SPE compared with normotensive controls (NC) and those with PE without CKD. Design and method: NC women (n = 19), women with PE (n = 14), CKD without SPE (n = 6) and with SPE (n = 11) were recruited from two tertiary antenatal clinics (mean ± SD 38 ± 3 weeks). Active renin and total AGT concentrations were measured by ELISA; urinary tetrahydroaldosterone was measured by gas chromatography-mass spectrometry; creatinine was measured using a standard clinical laboratory assay for normalisation. Results: Aldosterone and plasma active renin (Kruskal Wallis, both P < 0.05) were significantly different between groups. Aldosterone: creatinine ratios were significantly lower in both PE and SPE compared to the NC and women with CKD (median [IQR], PE: 6.5 [3, 14.4]; SPE: 10.8 [5.4, 16.4]; NC: 13.8 [9.1, 29.8]; CKD: 24.2 [16.3, 37.9] μg/mmol creatinine; P < 0.05 for all). Plasma active renin concentrations were also lower in PE, SPE and CKD women compared to NC women (PE: 5.3 [9.7, 21.8]; SPE: 3.4 [2.4, 12]; CKD: 3.9 [3.2, 6.2]; NC: 5.3 [0.2, 8.7] pg/ml; P < 0.05 for all). No differences in either plasma or urinary total AGT were observed between the groups. Conclusions: Women with SPE have lower urinary aldosterone and plasma active renin than women with CKD in keeping with women with PE without pre-existing kidney disease, suggestive of similar pathophysiology. Further exploration of the predictive value of low urinary aldosterone and plasma renin for adverse pregnancy events in women with CKD and its role in cases of diagnostic uncertainty is required.

Abstract P236: Site-1 Protease-derived Soluble (Pro) Renin Receptor Mediates Angiotensin II-induced Hypertension via Activation of Intrarenal Renin System

We have previously shown that collecting duct (CD)-specific deletion of (pro)renin receptor (PRR) attenuates angiotensin II (Ang II)-induced hypertension, accompanied with reduced soluble PRR (sPRR) that exerts antidiuretic action. Recent preliminary and published results demonstrated site-1portease (S1P) but not furin or ADMA19 as the predominant PPR cleavage enzyme. In the present study, we evaluated involvement of S1P-derived sPRR in Ang II-induced hypertension. By radiotelemetry, CD PRR KO mice exhibited reduced MAP on day 7 of Ang II infusion at 300 ng/kg/min as compared with floxed mice (MAP: 118±5 vs. 137±3 mmHg, N=5, p&lt;0.05). Administration of sPRR-His, a histidine-tagged sPRR, at 120 μg/kg/d via i.v. infusion to CD PRR KO mice for additional 7 days largely restored the sensitivity to Ang II (MAP: 139±6 mmHg in sPRR-His +Ang II group vs. 116±5 mmHg in Ang II group, N = 4, p&lt;0.05). The i.v. infusion was achieved via placement of a catheter in jugular vein with the other end connected to mimipump. In C57/BL6 mice, administration of a S1P inhibitor PF429242 (PF) via mini pump infusion at 30 mg/kg/d for 7 days attenuated Ang II-induced increases in MAP (day 7: 125±5 in Ang II+ PF group vs. 142±3 in Ang II group; N=6, p&lt;0.05), urinary sPRR excretion (27±4 vs. 63±9 pg/24h; N=6, p&lt;0.05). In parallel, urinary renin levels were elevated by Ang II, which was blunted by PF (renin activity: 0.17±0.03 in Ang II+PF vs. 0.80±0.081 in Ang II vs. 0.12±0.016 ng/24h in Control, N=6, p&lt;0.01; active renin content: 15.2±2.7 vs. 236.0±23.2 vs. 5.6±1.3 ng/24h, N=6, p&lt;0.01; prorenin content: 9.6±3.1 vs. 27.8±6.1 vs. 6.2±1.8 ng/24h, N=6, p&lt;0.05; total renin content: 24.8±5.2 vs. 263.8±27.0 vs. 11.8±3.0 ng/24h, N=6, p&lt;0.01). An intravenous infusion of sPRR-His counteracted the blood pressure-lowering effect of PF in Ang II-infused mice (MAP: 147±3 in PF+sPRR vs. 126±4 mmHg in PF; N=4, p&lt;0.05). Together, these results suggest that S1P-derived sPRR contributes to Ang II-induced hypertension through activation of intrarenal renin-angiotensin system.

Rapid Screening of Primary Aldosteronism by a Novel Chemiluminescent Immunoassay.

Measurement of plasma aldosterone and renin concentration, or activity, is useful for selecting antihypertensive agents and detecting hyperaldosteronism in hypertensive patients. However, it takes several days to get results when measured by radioimmunoassay and development of more rapid assays has been long expected. We have developed chemiluminescent enzyme immunoassays enabling the simultaneous measurement of both aldosterone and renin concentrations in 10 minutes by a fully automated assay using antibody-immobilized magnetic particles with quick aggregation and dispersion. We performed clinical validation of diagnostic ability of this newly developed assay-based screening of 125 patients with primary aldosteronism from 97 patients with essential hypertension. Results of this novel assay significantly correlated with the results of radioimmunoassay (aldosterone, active renin concentration, and renin activity) and liquid chromatography-tandem mass spectrometry (aldosterone). The analytic sensitivity of this particularly novel active renin assay was 0.1 pg/mL, which was better than that of radioimmunoassay (2.0 pg/mL). The ratio of aldosterone-to-renin concentrations of 6.0 (ng/dL per pg/mL) provided 92.0% sensitivity and 76.3% specificity as a cutoff for differentiating primary aldosteronism from essential hypertension. This novel measurement is expected to be a clinically reliable alternative for conventional radioimmunoassay and to provide better throughput and cost effectiveness in diagnosis of hyperaldosteronism from larger numbers of hypertensive patients in clinical settings.

322 - Ten minutes rapid measurement of aldosterone and active renin concentration may change the diagnosis and treatment of primary aldosteronism

322 - Ten minutes rapid measurement of aldosterone and active renin concentration may change the diagnosis and treatment of primary aldosteronism

PS 14-70 THE DEVELOPMENT OF ACCURATE 10 MINUTE MEASUREMENT OF ACTIVE RENIN AND ALDOSTERONE CONCENTRATION AND ITS CLINICAL SIGNIFICANCE

Objective: The measurement of plasma aldosterone concentration (PAC) and renin activity (PRA) or active renin concentration (ARC) is clinically important not only for detection of primary aldosteronism but also for the selection of antihypertensive agents to treat patients successfully. .However, it has taken approximately 7 days for clinicians to get the results. Of late, we developed the novel rapid non-RIA assays of PAC and ARC, which are measurable in 10 minutes. This study is intended to investigate the utility and accuracy of this new methods. Design and Method: Both PAC and ARC were simultaneously measured by chemiluminescent enzyme immunoassay (CLEIA) system machine with their specific monoclonal antibodies and were automatically washed by the immobilized magnetic particles. We retrospectively compared RIA-assayed PAC, PRA, ARC and LC-MS/MS-measured PAC with CLEIA-measured PAC and ARC in 290 patients with aldosterone producing adenoma (APA, n = 100), bilateral idiopathic hyperaldosteronism (IHA, n = 100) and essential hypertension (EH, n = 90). Results: CLEIA-measured PAC were significantly correlated with RIA-assayed PAC (y = 0.9846 x + 2.5708, Spearman's r = 0.9072, P < 0.0001), and also significantly correlated with LC-MS/MS PAC (y = 1.039x + 8.0, Spearman's r = 0.997, P < 0.0001). Rapid CLEIA-measured ARC with the lower detection limit of 0.25 pg/mL, which is very small as compared to 2 pg/mL in RIA-assayed ARC, were significantly correlated with RIA-assayed ARC (y = 1.0103 x + 0.9156, Spearman's r = 0.8166, P < 0.0001), and also significantly correlated with RIA-assayed PRA (Spearman's r = 0.8091 y = 4.4331 x + 0.4456, P < 0.0001). ARR-A and ARR-C of APA patients were 206 ± 21.7 and 64.5 ± 5.1 (Mean ± SEM), respectively. ARR-A and ARR-C of IHA patients were 42.8 ± 4.7 and 13.2 ± 0.9, and those of EH patients 15.4 ± 3.1 and 3.0 ± 0.5, respectively. Conclusions: Our ten minute measurement of PAC and ARC were proved to be very accurate and might be clinically useful.

Dose-effect relationship of perindopril 10, 14 and 20 mg assessed by urine and plasma AcSDKP levels in mildly sodium-depleted healthy volunteers

BackgroundWe describe a pharmacodynamic study of the dose-effect relationship of perindopril arginine at 10, 14, and 20mg with in vivo angiotensin-converting enzyme (ACE) activity, assessed by urine and plasma AcSDKP levels, as well as the effect on plasma active renin concentrations and blood pressure. MethodsThis randomized, double-blind, four-period, crossover study involved single-dose administration of perindopril arginine (10, 14, and 20mg or placebo) to 32 healthy male normotensive mildly sodium-depleted volunteers. Blood and urine were collected over 48h for AcSDKP, ACE activity, and plasma active renin measurements. ResultsThere were dose-related increases in urinary AcSDKP excretion and plasma AcSDKP concentration after administration of perindopril, with significant between-period differences (estimate of the median difference in urinary excretion over 48h of AcSDKP, 49.1 [95% CI: 15.3–82.0] nmol for 14 versus 10mg, and 73.2 [95% CI: 44.9–106.3] nmol for 20 versus 14mg). Consequently, a dose-dependent increase in plasma active renin concentration was observed. Even though each dose of perindopril 10 to 20mg was associated with a significant 24-h ambulatory blood pressure reduction versus placebo, no dose-dependency was detected in these normotensive subjects. ConclusionsAdministration of perindopril arginine 10, 14, or 20mg to mildly sodium-depleted healthy volunteers is associated with a dose-dependent inhibition of in vivo ACE activity with significant between-dose differences. This effect was associated with a dose-dependent increase in plasma active renin concentration, indicating a dose-dependent blockade of the renin angiotensin system.

Ten minutes simultaneous measurement of aldosterone and active renin concentration may lead to a proper selection of antihypertensive agents for the patients

Ten minutes simultaneous measurement of aldosterone and active renin concentration may lead to a proper selection of antihypertensive agents for the patients

Abstract P178: Vitamin D Biomarkers with Risk of Hypertension and Renin-Angiotensin System

Background: Experimental studies suggest that vitamin D may potentially prevent the development of hypertension through down-regulation of the renin-angiotensin system. However, evidence from epidemiologic studies remains limited. Objective: In parallel nested case-control studies of women from the Women’s Health Study (WHS) and men from the Physicians’ Health Study (PHS) with &gt;10 years follow-up, we examined the prospective associations between the circulating biomarkers of vitamin D status with risk of hypertension, as well as the inter-relation between vitamin D biomarkers and renin production. Methods: In each cohort, 500 incident hypertension cases and 500 controls were randomly selected from participants who were free of cardiovascular disease, cancer, and hypertension and provided bloods at baseline. Hypertension cases were identified based on self-reported blood pressure, physician’s diagnosis, or medication use. Controls were matched to cases on gender, age, race, follow-up time, and month of blood draw. Baseline plasma 25(OH)-vitamin D, parathyroid hormone (PTH), and total renin (pro-renin plus active renin) concentrations were measured. Analyses were first performed in each cohort separately and, given the similar results, finally combined for both cohorts. Results: Baseline concentrations of 25(OH)-vitamin D (mean of 26.6 vs. 27.0 ng/mL) and PTH (32.6 vs. 32.2 pg/mL) were similar in hypertension cases and controls. In the crude matched model, the risk of hypertension did not change with 25(OH)-vitamin D or PTH concentrations. Additional adjustment for other known hypertension-related risk factors minimally affected the associations. After adjusting for baseline smoking, alcohol use, exercise, menopausal status and hormone therapy use among women, body mass index, and history of diabetes and hypercholesterolemia, the relative risks of incident hypertension across increasing quintiles of 25(OH)-vitamin D were 1.00, 1.42 (95% CI: 0.94-2.16), 0.94 (95% CI: 0.60-1.48), 0.99 (95% CI: 0.61-1.61), and 1.03 (95% CI: 0.63-1.69) (p, trend, 0.48), and across increasing quintiles of PTH were 1.00, 1.26 (95% CI: 0.83-1.92), 0.91 (95% CI: 0.60-1.40), 1.10 (95% CI: 0.70-1.71), 0.92 (95% CI: 0.59-1.44) (p, trend, 0.50). These associations were similar in men and women. Among controls, plasma 25(OH)-vitamin D was inversely correlated with PTH (Pearson r: -0.24, p&lt;0.0001), while neither 25(OH)-vitamin D (r: -0.02, p=0.53) nor PTH (r: -0.01, p=0.69) was correlated with total renin concentrations. Conclusions: In prospective cohorts of men and women, we found no association between either baseline plasma 25(OH)-vitamin D or PTH with the risk of hypertension, or between either 25(OH)-vitamin D or PTH with total renin concentration. More research is needed to further elucidate the specific effect of vitamin D in the development of hypertension.

Prospective validation of an automated chemiluminescence-based assay of renin and aldosterone for the work-up of arterial hypertension.

The availability of simple and accurate assays of plasma active renin (DRC) and aldosterone concentration (PAC) can improve the detection of secondary forms of arterial hypertension. Thus, we investigated the performance of an automated chemiluminescent assay for DRC and PAC in referred hypertensive patients. We prospectively recruited 260 consecutive hypertensive patients referred to an ESH Center for Hypertension. After exclusion of six protocol violations, 254 patients were analyzed: 67.3% had primary hypertension, 17.3% an aldosterone producing adenoma (APA), 11.4% idiopathic hyperaldosteronism (IHA), 2.4% renovascular hypertension (RVH), 0.8% familial hyperaldosteronism type 1 (FH-1), 0.4% apparent mineralocorticoid excess (AME), 0.4% a renin-producing tumor, and 3.9% were adrenalectomized APA patients. Bland-Altman plots and Deming regression were used to analyze results. The diagnostic accuracy (area under the curve, AUC of the ROC) of the DRC-based aldosterone-renin ratio (ARRCL) was compared with that of the PRA-based ARR (ARRRIA) using as reference the conclusive diagnosis of APA. At Bland-Altman plot, the DRC and PAC assay showed no bias as compared to the PRA and PAC assay. A tight relation was found between the DRC and the PRA values (concordance correlation coefficient=0.92, p<0.0001) and the PAC values measured with radioimmunoassay and chemiluminescence (concordance correlation coefficient=0.93, p<0.001). For APA identification the AUC of the ARRCL was higher than that of the ARRRIA [0.974 (95% CI 0.940-0.991) vs. 0.894 (95% CI 0.841-0.933), p=0.02]. This rapid automated chemiluminescent DRC/PAC assay performed better than validated PRA/PAC radioimmunoassays for the identification of APA in referred hypertensive patients.