Changes In Plasma Aldosterone Levels Research Articles

Efficacy and safety of adrenal arterial embolization for primary aldosteronism: a systematic review and meta-analysis.

Primary aldosteronism (PA) is related with resistant hypertension and cardiovascular events. Adrenal artery embolization (AAE) is a choice for patients who refused surgery and medical therapy. However, whether AAE can effectively and safely treat PA is unclear. We performed this meta-analysis to determine the efficacy and safety of AAE for patients with PA. Databases including Cochrane Library, Embase, PubMed and Web of Science were used to obtain relevant articles published before July 30, 2023. The primary outcome was blood pressure before and after AAE. The second outcomes included changes in plasma aldosterone level, serum potassium level, and plasma cortisol level. Finally, 7 prospective studies with 222 patients were included. The results showed that systolic and diastolic blood pressure was reduced by 21.68 mmHg (P<0.001) and 10.54 mmHg (P=0.007) respectively after AAE. The change in plasma aldosterone and serum potassium level was -11.52 ng/dL and 0.61 mmol/L respectively (P<0.001), whereas the reduction in cortisol level was not apparent. Moreover, AAE is a relatively safe procedure which only causes some minor complications such as back pain and fever. This meta-analysis indicated that AAE could effectively and safely treat PA. It is a good choice for patients that are not suitable for adrenalectomy or drug therapy.

Adrenal Corticosteroid Perturbation by the Endocrine Disruptor BDE-47 in a Human Adrenocortical Cell Line and Male Rats.

Polybrominated diphenyl ethers (PBDEs) have been previously shown to alter various endocrine biosynthetic pathways. Growing epidemiological evidence suggests that PBDEs alter cardiovascular function. The goal of this study was to examine the effects of BDE-47 on adrenal corticosteroid pathways that play vital roles in cardiovascular homeostasis and pathophysiology. The effect of BDE-47 on aldosterone and cortisol secretion was characterized in a human adrenocortical cell line. HAC15 cells were exposed to various concentrations of BDE-47 (1 nM to 100 μM). Cell viability, corticosteroid secretion, gene expression of enzymes involved in corticosteroid synthesis, and metabolic activity was examined. Additionally, Sprague Dawley male rats were orally exposed to BDE-47 (10 or 100 µg/kg), 5 days per week for 16 weeks. Organ weights and plasma corticosteroid levels were measured. In HAC15 cells, basal and stimulated aldosterone and cortisol secretion was significantly increased by BDE-47. Gene expression of several enzymes involved in corticosteroid synthesis and mitochondrial metabolism also increased. In Sprague Dawley rats, adrenal but not heart, kidney, or liver weights, were significantly increased in BDE-47 treatment groups. Plasma corticosterone levels were significantly increased in the 100 µg BDE-47/kg treatment group. No change in plasma aldosterone levels were observed with BDE-47 exposure. These data indicate that BDE-47 disrupts the regulation of corticosteroid secretion and provides further evidence that PBDEs are potential endocrine disruptors. Future studies will determine the underlying molecular mechanism of altered corticosteroid production and examine whether these alterations result in underlying cardiovascular disease in our rodent model of 16-week BDE-47 exposure.

P1017A RANDOMIZED, PLACEBO-CONTROLLED MULTICENTER STUDY OF THE EFFECTS OF 12 WEEKS OF SODIUM ZIRCONIUM CYCLOSILICATE (SZC) ON ALBUMINURIA (UACR) IN PATIENTS WITH TYPE 2 DIABETES AND HYPERKALEMIA

Abstract Background and Aims Hyperkalemia is a frequent challenge in the treatment of type 2 diabetes and chronic kidney disease. It often leads to suboptimal dosing or discontinuation of renin-angiotensin (RAS) blockade, thus increasing the risk of renal disease progression. Furthermore, epidemiological findings indicate that high potassium levels impair the renoprotective effect of RAS blockade. We want to test whether adjunctive treatment with sodium zirconium cyclosilicate (SZC) a new treatment for hyperkalemia, improves the effect of standard RAS blocking treatment as measured by urinary albumin creatinine ratio (UACR) in individuals with type 2 diabetes. Method Randomized, double-blind placebo-controlled multicenter study with 2 sites in Denmark and 3 sites in Sweden. Individuals (n=100) with type 2 diabetes (age 18-85), persistent macroalbuminuria (UACR≥ 200 mg/g) on chronic RAS blocking treatment and documented hyperkalemia (plasma potassium ≥ 5.0 mmol/L at least once within 90 days of inclusion) will be enrolled in the study. Participants with plasma potassium &amp;gt;5.0 mmol/L at the last assessment before randomization will be randomized to receive SZC 10 g or placebo three times a day (tid) for 2 days followed by SZC 5g or placebo once a day (qd). Participants with serum potassium ≤ 5.0 mmol/L will be randomized to receive SZC qd or placebo qd.UACR will be measured in three consecutive morning spot urine collections at baseline and the end of study after 12 weeks of treatment with Lokelma or placebo. Results The primary outcome is change in geometric mean UACR from baseline to end of studySecondary outcomes include changes in estimated glomerular filtration rate (eGFR, calculated by CKD-EPI formula) and 24-h urinary sodium and potassium excretion.In an exploratory analysis the long-term effect of potassium reduction will be modelled using the PRE-SCORE risk calculator. In addition, changes in plasma aldosterone levels will be assessed, and safety will be monitored according to good clinical practice. Conclusion This study will test the concept of SZC as an add-on therapy to improve the renoprotective effect of standard RAS blocking treatment. This could provide future potential for keeping more individuals on optimal dosing of RAS blockade.

Plasma Aldosterone Levels Are Not Associated With Cardiovascular Events Among Patients With High-Risk Vascular Disease: Insights From the ACCELERATE Trial.

BackgroundThe failure of cholesteryl ester transfer protein inhibitor torcetrapib was associated with an off‐target increase in plasma aldosterone. We sought to evaluate the impact of evacetrapib on plasma aldosterone level and determine the association between plasma aldosterone level and major adverse cardiovascular events among patients with stable high‐risk vascular disease enrolled in the ACCELERATE (Assessment of Clinical Effects of Cholesteryl Ester Transfer Protein Inhibition With Evacetrapib in Patients at a High Risk for Vascular Outcomes) trial.Methods and ResultsWe included all patients with a plasma aldosterone level (N=1624) and determined the impact of evacetrapib exposure compared with placebo on plasma aldosterone levels after 12 months of treatment. Using baseline and postexposure aldosterone levels, hazard ratios for major adverse cardiovascular events (cardiovascular death, nonfatal myocardial infarction, cerebrovascular accident, hospitalization for unstable angina, and revascularization) with increasing quartile of baseline and percentage change in plasma aldosterone level at follow‐up were calculated. The average age was 65.2 years, 75.7% were men, 93.7% were hypertensive, 73.3% were diabetic, and 57.6% had a prior myocardial infarction. Baseline plasma aldosterone level (85.2 [43, 150] versus 86.8 [43, 155] pmol/L; P=0.81) and follow‐up percentage change (13.6% [−29, 88] versus 17.9% [−24, 87]; P=0.23) were similar between those who received evacetrapib and placebo. During median follow‐up of 28 months, major adverse cardiovascular events occurred in 263 patients (16.2%). The hazard ratios for increasing quartile of baseline or percentage change in plasma aldosterone level at follow‐up were not significant for major adverse cardiovascular events. These findings remained consistent when adjusting for significant characteristics.ConclusionsExposure to evacetrapib did not result in significant change in plasma aldosterone levels compared with placebo. Among patients with stable high‐risk vascular disease, plasma aldosterone levels were not a predictor for future cardiovascular events.Clinical Trial Registration URL: http://www.ClinicalTrials.gov. Unique identifier: NCT01687998.

Treatment of Primary Aldosteronism with mTORC1 Inhibitors

CONTEXT Mammalian target of rapamycin complex 1 (mTORC1) activity is often increased in the adrenal cortex of patients with primary aldosteronism (PA), and mTORC1 inhibition decreases aldosterone production in adrenocortical cells, suggesting the mTORC1 pathway as a target for treatment of PA. OBJECTIVE To investigate the effect of mTORC1 inhibition on adrenal steroid hormones and hemodynamic parameters in mice and in patients with PA. DESIGN (i) Plasma aldosterone, corticosterone, and angiotensin II (Ang II) were measured in mice treated for 24 hours with vehicle or rapamycin. (ii) Plasma aldosterone levels after a saline infusion test, plasma renin, and 24-hour urine steroid hormone metabolome and hemodynamic parameters were measured during an open-label study in 12 patients with PA, before and after 2 weeks of treatment with everolimus and after a 2-week washout. MAIN OUTCOME MEASURES (i) Change in plasma aldosterone levels. (ii) Change in other steroid hormones, renin, Ang II, and hemodynamic parameters. RESULTS Treatment of mice with rapamycin significantly decreased plasma aldosterone levels (P = 0.007). Overall, treatment of PA patients with everolimus significantly decreased blood pressure (P < 0.05) and increased renin levels (P = 0.001) but did not decrease aldosterone levels significantly. However, prominent reduction of aldosterone levels upon everolimus treatment was observed in four patients. CONCLUSION In mice, mTORC1 inhibition was associated with reduced plasma aldosterone levels. In patients with PA, mTORC1 inhibition was associated with improved blood pressure and renin suppression. In addition, mTORC1 inhibition appeared to reduce plasma aldosterone in a subset of patients.

Primary aldosteronism and impaired natriuresis in mice underexpressing TGFβ1

To uncover the potential cardiovascular effects of human polymorphisms influencing transforming growth factor β1 (TGFβ1) expression, we generated mice with Tgfb1 mRNA expression graded in five steps from 10% to 300% normal. Adrenal expression of the genes for mineralocorticoid-producing enzymes ranged from 50% normal in the hypermorphs at age 12 wk to 400% normal in the hypomorphs accompanied with proportionate changes in plasma aldosterone levels, whereas plasma volumes ranged from 50% to 150% normal accompanied by marked compensatory changes in plasma angiotensin II and renin levels. The aldosterone/renin ratio ranged from 0.3 times normal in the 300% hypermorphs to six times in the 10% hypomorphs, which have elevated blood pressure. Urinary output of water and electrolytes are markedly decreased in the 10% hypomorphs without significant change in the glomerular filtration rate. Renal activities for the Na(+), K(+)-ATPase, and epithelial sodium channel are markedly increased in the 10% hypomorphs. The hypertension in the 10% hypomorphs is corrected by spironolactone or amiloride at doses that do not change blood pressure in wild-type mice. Thus, changes in Tgfb1 expression cause marked progressive changes in multiple systems that regulate blood pressure and fluid homeostasis, with the major effects being mediated by changes in adrenocortical function.

Improvement of insulin resistance, blood pressure and interstitial pH in early developmental stage of insulin resistance in OLETF rats by intake of propolis extracts

Propolis, a resinous mixture collected from plants by the Apis mellifera bee, contains high level nutrient factors including vitamins, polyphenols, and amino acids that would be expected to improve insulin sensitivity. Insulin resistance would secondarily cause elevation of blood pressure and increase the risk of cardiovascular diseases. The purpose of this study is to investigate the effect of propolis extracts on blood glucose levels and blood pressures in an early developmental stage of insulin resistance in Otsuka Long-Evans Tokushima Fatty (OLETF) rats. OLETF rats (10weeks old) were divided into three different groups: normal diet, 0.1% propolis diet, and 0.5% propolis diet. After 8weeks, blood glucose levels, blood pressures, plasma metabolic factors and hormones, and interstitial fluid pH were measured. Casual blood glucose levels were decreased associated with a reduction of plasma insulin levels in both propolis diet groups compared with normal diet group. Propolis decreased systolic blood pressure with no significant changes in plasma aldosterone levels. We also found that interstitial fluid pH in ascites, liver, and skeletal muscle was higher in rats fed propolis diet than rats fed normal diet. These data suggests that dietary propolis improves insulin sensitivity and blood pressures in the early stage of the process in development of insulin resistance, which may be mediated by suppression of metabolic acidosis.

The contributions of muscarinic receptors and changes in plasma aldosterone levels to the anti-hypertensive effect of Tulbaghia violacea

BackgroundTulbaghia violacea Harv. (Alliaceae) is used to treat various ailments, including hypertension (HTN) in South Africa. This study aims to evaluate the contributions of muscarinic receptors and changes in plasma aldosterone levels to its anti-hypertensive effect.MethodsIn the acute experiments, methanol leaf extracts (MLE) of T. violacea (30–120 mg/kg), muscarine (0.16 -10 μg/kg), and atropine (0.02 - 20.48 mg/kg), and/or the vehicle (dimethylsulfoxide (DMSO) and normal saline (NS)) were respectively and randomly administered intravenously in a group of spontaneously hypertensive (SHR) weighing 300 to 350 g and aged less than 5 months. Subsequently, T. violacea (60 mg/kg) or muscarine (2.5 μg/kg) was infused into eight SHRs, 20 min after atropine (5.12 mg/kg) pre-treatment. In the chronic (21 days) experiments, the SHRs were randomly divided into three groups, and given the vehicle (0.2 ml/day of DMSO and NS), T. violacea (60 mg/kg/day) and captopril (10 mg/kg/day) respectively into the peritoneum, to investigate their effects on blood pressure (BP), heart rate (HR), and plasma aldosterone levels. Systolic BP and HR were measured using tail-cuff plethysmography during the intervention. BP and HR were measured via a pressure transducer connecting the femoral artery and the Powerlab at the end of each intervention in the acute experiment; and on day 22 in the chronic experiment.ResultsIn the acute experiments, T. violacea, muscarine, and atropine significantly (p < 0.05) reduced BP dose-dependently. T. violacea and muscarine produced dose-dependent decreases in HR, while the effect of atropine on HR varied. After atropine pre-treatment, dose-dependent increases in BP and HR were observed with T. violacea; while the BP and HR effects of muscarine were nullified. In the chronic experiments, the T. violacea-treated and captropril-treated groups had signicantly lower levels of aldosterone in plasma when compared to vehicle-treated group. Compared to the vehicle-treated group, significant reduction in BP was only seen in the captopril-treated group; while no difference in HR was observed among the groups.ConclusionThe results obtained in this study suggest that stimulation of the muscarinic receptors and a reduction in plasma aldosterone levels contribute to the anti-hypertesive effect of T. violacea.

Can the blood pressure effects of COX-2 selective inhibitors be explained by changes in plasma aldosterone levels?

The increased cardiovascular risk associated with rofecoxib may relate to differential effects on blood pressure (BP) in comparison with other cyclooxygenase-2 (COX-2) selective inhibitors. Rofecoxib is uniquely metabolized by cytosol reductase and may compete with aldosterone for metabolism. We hypothesized that the effect of rofecoxib on BP may be due to an increase in aldosterone levels. Prospective, randomized, cross-over study. Tertiary institution. Eleven patients (all female, age 65 +/- 11 years) with osteoarthritis and hypertension. Patients received rofecoxib 50 mg once/day or celecoxib 400 mg once/day for 8 weeks, followed by cross-over after a 2-week wash-out period. Office BP, heart rate (HR), plasma aldosterone and aldosterone related-markers, markers of sympathetic and parasympathetic activity, catecholamines and heart rate variability (HRV) were measured. Rofecoxib caused an increase in BP compared to celecoxib; a change in recumbent systolic BP +/- SD (6.1 +/- 11.0 versus -7.0 +/- 12.5 mmHg, P < 0.05) and recumbent diastolic BP +/- SD (3.6 +/- 7.6 versus -1.7 +/- 5.7 mmHg). There was no difference in median change in plasma aldosterone levels between rofecoxib and celecoxib (-31 +/- 171.5 versus 43 +/- 147 pg/ml, P = 0.173). The other parameters measured were not different between the two agents. Rofecoxib therapy results in a significant increase in systolic BP compared to celecoxib. As plasma aldosterone levels were not different between the two drugs, the differential effect of rofecoxib on BP compared to celecoxib appears to be unlikely due to competition by rofecoxib for aldosterone metabolism.

Influence of the CYP11B2 -344C/T polymorphism on plasma aldosterone, sodium excretion and blood pressure responses to aerobic exercise training in middle-aged to older prehypertensives

Aldosterone influences renal Na+ handling and normal blood pressure (BP) regulation but if consistently elevated, aldosterone may contribute to the development of hypertension. A few studies have found that as with BP, plasma aldosterone (PA) levels can change with aerobic exercise training (AEX) in hypertensives, but the response of these phenotypes to AEX vary by individual. The CYP11B2 (-344C/T) gene polymorphism has been associated with variability in both blood pressure and urinary and PA levels among hypertensives and may help explain the response of these phenotypes to AEX. The purpose of this study was to determine if the -344C/T polymorphism was associated with changes in PA levels, 24-hour Na+ excretion and BP after 6 months of AEX in middle-aged to older White prehypertensives. 23 Caucasian disease free, sedentary prehypertensives completed a standardized AEX program. All participants followed the AHA Step 1 diet. Blood samples were collected under fasting and supine conditions and PA was measured by RIA. The T and C allele frequencies were 0.61 and 0.39, respectively. There were 9 participants in the TT genotype group and 13 in the TC+CC genotype group. The TC+CC genotype group tended to decrease PA levels (−39±21 pg/ml, p=0.09) and had a greater reduction in PA levels with AEX than the TT genotype group after accounting for baseline plasma aldosterone levels (TC+CC −47±8 pg/ml; TT: −23±10 pg/ml, p<0.001). The TC+CC genotype group significantly decreased systolic BP (−4±2 pg/ml, p=0.03) and had a greater reduction in systolic BP with AEX than the TT genotype group after accounting for baseline systolic BP (TC+CC −4±1pg/ml; TT: −2±2 mm Hg, p<0.02). Neither genotype group changed diastolic BP or 24 hour Na+ excretion and there was no difference in the change in diastolic BP and 24-hour Na+ excretion between the two genotype groups. Based on this preliminary evidence, the presence of the C allele among prehypertensives is associated with a greater reduction in plasma aldosterone and systolic BP with AEX.

Inhibition of aldosterone turn-off phenomenon following chronic adrenocorticotropin treatment with in vivo administration of antiglucocorticoid and antioxidants in rats.

Chronic adrenocorticotropin (ACTH) treatment in rats leads to a fall in aldosterone secretion (aldosterone turn-off or "aldosterone escape" phenomenon) with a concomitant rise in corticosterone. To elucidate whether ACTH-induced aldosterone suppression is mediated by steroid type II receptor or related to a free-radical effect by over-synthesized corticosterone, we examined the effects of a glucocorticoid antagonist, RU486, and antioxidants dimethyl sulfoxide (DMSO) and vitamin E, on the aldosterone turn-off phenomenon in rats. Each rat received daily for 5 days a different dose of ACTH-Z (5, 10, 20 or 40 micrograms/100 g body weight) 1 mg RU486/100 g body weight, 100 microliters (1.3 mmol) DMSO/100 g body weight or 2 mg vitamin E/100 g body weight with subcutaneous injection. Plasma steroid levels and in vitro release of steroids from the adrenal capsule were measured. The ACTH-Z treatment caused a dose-dependent increase in corticosterone and a decrease in aldosterone in both plasma and adrenal capsule experiments, as well as an increase in adrenal weights. For the following study 5 micrograms/100 g body weight of ACTH-Z was used. Administration of RU486 alone caused no change in plasma aldosterone level compared to controls, even though the steroid type II receptor was blocked, as evidenced by significant increases in plasma ACTH and corticosterone levels. Concomitant administration of RU486 and ACTH-Z increased both plasma corticosterone and aldosterone levels (p < 0.01) but decreased adrenal capsule corticosterone production (p < 0.05) compared to the rats treated with ACTH-Z alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal response to 7 days of lower body positive pressure in squirrel monkeys

The purpose of this study was to characterize the renal response to central volume expansion using lower body positive pressure (LBPP) in the adult male squirrel monkey (Saimiri sciureus). Urinary excretion of sodium, potassium, and water and plasma aldosterone concentrations were measured during a control day, 7 days of LBPP, and a recovery day. Time control experiments in the same animals included chair sitting without exposure to LBPP. Seven monkeys (600-1,000 g) were trained to sit in a specially designed metabolism chair before chronic implantation of arterial and venous catheters to facilitate maintenance infusion of saline, monitoring of vascular pressures, and blood sampling; urine was collected via a condomlike tube. A cephalad shift in body fluid was induced by applying 20 mmHg of air pressure from the waist down. Urine volume and sodium excretion were increased significantly (28 to 52 ml/day and 0.4 to 3.5 meq/day, respectively) during the initial 24 h of LBPP with most of this response occurring in the first 6-12 h. From the 2nd to the 7th day of LBPP, urinary excretion rates for sodium and water were not different from chair-sitting controls. Water and sodium balance significantly decreased from +15 to -12 ml/day and from +1.1 to -2.2 meq/day, respectively, from the control to the first day of LBPP. This change in balance was not observed in the time-control group. Removal of the stimulus resulted in a modest conservation of sodium and water. The renal responses were not associated with any changes in plasma aldosterone levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Peptide Infusion in Primary Aldosteronism: Renal, Hemodynamic and Hormonal Effects

We have previously shown that a bolus injection of alpha-human atrial natriuretic peptide (alpha-h-ANP) (100 micrograms) in patients with primary aldosteronism induces a transient decrease of blood pressure and a marked natriuresis, but no changes in plasma aldosterone levels. Eight additional cases were studied with a different protocol. Alpha-h-ANP was infused at the dose of 50 ng/kg/min over 1 h, after a bolus of 50 micrograms; saline alone was infused as control. Blood pressure, heart rate, plasma aldosterone, plasma renin activity, cortisol, serum and urinary Na and K and urinary volume were measured. A slight fall in blood pressure, without heart rate changes, was obtained within the first 5 min; this lasted throughout the infusion and for 1 h afterwards. Urinary volume and urinary sodium were significantly higher than controls during the first 2 h, while urinary potassium slightly increased only during the first hour. Plasma renin activity remained suppressed. Plasma aldosterone levels were similar throughout the infusion. Cortisol was not significantly different than placebo except that there was a significant rise after stopping ANP. These data confirm the potent natriuretic effect of ANP infusion and the lack of correlation between ANP induced natriuresis and the effect of ANP on aldosterone in patients with primary aldosteronism.

Effects of Ciclosporin on Plasma Renin Activity, Catecholamines and Prostaglandins in Patients with Idiopathic Uveitis

Animals and humans undergoing treatment with ciclosporin (CS) show a reversible increase in renal vascular resistance and a decrease in glomerular filtration rate. The causes of these abnormalities have not yet been established. We evaluated the effects of a 1-week treatment with CS on creatinine clearance, renal arachidonic acid metabolites, plasma renin activity (PRA), plasma aldosterone levels, urinary excretion and plasma levels of catecholamines in 7 patients with idiopathic uveitis. We show that CS treatment induces a significant (p less than 0.05) decrease in creatinine clearance (from 132 +/- 0.5 to 108 +/- 8 ml/min); urinary 6-keto-PGF1 excretion (from 17.8 +/- 4.9 to 10.9 +/- 3.3 ng/mmol creatinine), urinary thromboxane B2 excretion (from 7.0 +/- 1.0 to 3.6 +/- 0.9 ng/mmol creatinine), upright PRA (from 4.2 +/- 0.9 to 2.3 +/- 0.8) and supine PRA (from 2.0 +/- 0.5 to 1.1 +/- 0.3). We found no change in plasma aldosterone levels and plasma levels and urinary excretion of catecholamines. We suggest that the reversible renal vasoconstriction observed in patients treated with CS may be induced by inhibition of renal prostacyclin synthesis. In this setting inhibition of PRA and angiotensin II formation may impair autoregulation of effective filtration pressure and therefore glomerular filtration rate.

Role of atrial natriuretic peptide in natriuresis in volume-expanded rats.

Continuous intravenous infusion of rat atrial natriuretic peptide (rANP) was carried out for 60 min in urethan-anesthetized rats. Plasma rANP (PANP) levels during 0, 12.5, and 50 ng/min rANP infusion reached 20.9 +/- 3.4, 61.2 +/- 12.3, and 228 +/- 30.6 pg/ml, respectively. Urinary sodium excretion (UNaV) remained unchanged during the 0 and 12.5 ng/min rANP infusion. In contrast, the 50 ng/min rANP infusion resulted in a 5.6-fold increase in UNaV without significant changes in plasma aldosterone levels and glomerular filtration rate. Isotonic saline infusion (116 microliter/min for 60 or 120 min) caused a significant increase in UNaV. UNaV in an experimental model of the syndrome of inappropriate antidiuretic hormone secretion (SIADH) was 5.0 times greater than in control animals. PANP levels in 60- or 120-min saline-infused and SIADH rats were 46.3 +/- 6.7, 39.0 +/- 9.0, and 35.6 +/- 3.2 pg/ml, respectively. These values were significantly higher than control values but failed to achieve a level at which natriuresis occurred during the infusion of rANP. These results suggest that endogenous ANP may not play a critical role in the induction of acute natriuresis in volume-expanded states, although it could be partially involved in such a natriuretic response.

Potassium-Lowering Effect of Albuterol for Hyperkalemia in Renal Failure

To study the effect of specific beta 2-adrenergic stimulation on potassium metabolism in renal failure, we intravenously administered albuterol (Salbutamol) sulfate, 0.5 mg, to 20 patients with chronic renal failure (glomerular filtration rate, less than 5 mL/min) receiving maintenance hemodialysis. Within 30 minutes after albuterol administration, serum potassium level dropped from 5.6 +/- 0.2 (+/- SEM) to 4.5 +/- 0.2 mEq/L (5.6 +/- 0.2 to 4.5 +/- 0.2 mmol/L). There were no changes in plasma aldosterone levels or arterial pH, but blood glucose and serum insulin levels increased. Albuterol, however, induced similar decreases in serum potassium levels in three diabetic patients while free C peptide levels remained undetectable or subnormal after administration of the drug. Albuterol sulfate alone (0.5 mg intravenously) was also used to treat 24 patients with acute or chronic renal failure and hyperkalemia. Their serum potassium levels dropped from 7 +/- 0.2 mEq/L (7 +/- 0.2 mmol/L) to 5.6 +/- 0.2 mEq/L (5.6 +/- 0.2 mmol/L), 5.6 +/- 0.2 mEq/L (5.6 +/- 0.2 mmol/L), 6 +/- 0.2 mEq/L (6 +/- 0.2 mmol/L), and 6.2 +/- 0.2 mEq/L (6.2 +/- 0.2 mmol/L) at 30, 60, 180, and 360 minutes after receiving albuterol, respectively, and this was accompanied by reversal of the electrocardiographic manifestations of hyperkalemia. Despite inducing transient tachycardia, albuterol was remarkably well tolerated and no serious side effects were observed. beta 2-adrenergic stimulation of intracellular potassium uptake by albuterol is a safe and effective alternative for the treatment of hyperkalemia in renal failure.

Lack of effect of cimetidine on the renin-angiotensin-aldosterone system in man.

It is widely accepted that angiotensin II, ACTH and potassium are the major factors controlling the release of aldosterone. Conflicting results have been reported about the role of serotonin, dopamine and histamine. To evaluate the possible involvement of H2-histaminergic receptors, the effect of intravenous injection of 400 mg cimetidine on the renin-angiotensin-aldosterone system has been evaluated in 10 healthy volunteers. The administration of cimetidine did not induce a significant change in plasma aldosterone level or in its major controlling factors.

Discrepancy between antihypertensive effect and angiotensin converting enzyme inhibition by captopril.

Captopril, an inhibitor of angiotensin converting enzyme, was administered twice daily to 13 hypertensive patients for a mean period of 9 weeks. Continuous blood pressure control in the ambulatory patients was established with a portable blood pressure recorder. Notwithstanding, in eight patients with normal renal function, plasma converting enzyme was found to resume normal activity before administration of the morning dose of captopril. Only in 5 patients with impaired renal function did some blockade of plasma converting enzyme persist for more than 12 hours. Measured plasma converting enzyme activity seemed to reflect total conversion of angiotensin I, including conversion in the pulmonary vascular bed, since changes in its activity were closely paralled by changes in plasma aldosterone levels. Bradykinin accumulation seems unlikely when converting enzyme and thus, presumably, kininase II has resumed normal activity. Captopril administration does not seem to alter plasma epinephrine or norepinephrine levels. Blood pressure reduction in the face of normal angiotensin converting enzyme activity is probably due to hyporesponsiveness of the arterioles to pressor hormones, which may be due to specific renin-related and/or nonspecific effects of captopril.

Effect of adrenalectomy on medullary collecting-duct function in rats before and during blood volume expansion.

Adrenalectomized rats, kept on tap water for 3 days and infused with the glucocorticoid dexamethasone during the experiment, were compared to similarly treated sham-operated rats. Using the microcatheterization technique, reabsorption of fluid, sodium and potassium in the medullary collecting duct was studied before and after infusion of donor blood (2.3% of body weight). Before intravascular volume expansion sodium excretion in adrenalectomized rats was greater than in sham-operated ones. Extensive overlap between the two groups made this difference not statistically significant. However, the fraction of filtered sodium excreted was significantly greater after adrenalectomy, indicating the expected tubular transport defect. Fluid reabsorption from the medullary collecting-duct system was comparable in both series. Adrenalectomy did not inhibit net sodium reabsorption from the inner medullary duct, although reduction of Na transport in the outer medullary collecting system could be inferred. Renal excretion of potassium was not associated with net K secretion in the collecting duct in either group. During hypervolemia induced by intravenous infusion of donor blood, marked diuresis, natriuresis and kaliuresis were observed in all animals, associated with inhibition of net fluid and sodium reabsorption along the collecting system in both inner and outer medulla. Small, but statistically significant secretion of potassium became evident. The relatively reduced renal response in adrenalectomized animals could be attributed in part to a decreased filtered load compared to sham-operated rats. It is concluded: (1) that lack of mineralocorticoid does not prevent the normal fluid and sodium reabsorption from the lumen of the inner medullary collecting system, and (2) that the inhibition of this reabsorption consequent to hypervolemia is independent of changes in plasma aldosterone levels.

Circadian rhythm of renin and aldosterone in unilateral renovascular hypertension. Pre- and post-operative studies.

The circadian rhythm of plasma renin activity and plasma aldosterone levels was determined in 11 normal subjects and 7 patients with unilateral renovascular hypertension, while upright and while recumbent. Plasma renin activity tended to be higher in patients with unilateral renovascular hypertension than in the normal subjects. Every patient with unilateral renovascular hypertension had an elevated plasma renin activity with 12 hours of upright posture. Changes in plasma aldosterone levels were not as striking. Three patients were restudied after surgical correction of their unilateral renovascular hypertension: the circadian rhythm had returned to normal, and the plasma renin activity and plasma aldosterone levels had decreased from preoperative values. These results suggest that chronic unilateral renovascular hypertension is associated with activation of the renin-angiotensin-aldosterone system, which results in increased circulating levels of plasma renin activity (at least during certain times of the day), when carefully tested.