There is increasing evidence for rapid nongenomic effects of aldosterone. Aldosterone has been demonstrated to alter intracellular pH and calcium in isolated cells. However, few studies have correlated these effects with aldosterone-mediated physiological responses. Therefore, we studied rapid effects of aldosterone on vascular reactivity, intracellular Ca2+, and pH in resistance vessels. Furthermore, we explored whether the new antimineralocorticoid drug eplerenone could effectively block nongenomic aldosterone-mediated effects. The vasoconstrictor action of aldosterone was examined directly by determining the diameter of small resistance mesenteric vessels (160-200 microm resting diameter), simultaneously with intracellular pH or Ca2+. Aldosterone (10 nm) caused a rapid constriction of resistance vessels (8.1% +/- 1.0% reduction in the diameter below control conditions, P < 0.05). Aldosterone potentiated phenylephrine-mediated constriction in small and large mesenteric vessels. Aldosterone induced a rapid increase of intracellular Ca2+ and cellular alkalinization. Vasoconstrictor action of aldosterone and nongenomic effects on the sodium-proton exchanger (NHE1) activity or intracellular Ca2+ responses was abolished by eplerenone. The vasoconstrictor response of aldosterone was related to phosphatidylinositol 3-kinase (PI3-K): the hormone decreased protein kinase B phosphorylation; pharmacological inhibition of PI3-K (10 microm LY294002 or 1 microm wortmannin) increased arterial contractility. Inhibitors of ERK 1/2 phosphorylation (15 microm PD98059) had no effect on aldosterone-mediated vasoconstriction. Inhibition of protein kinase C with 1 microm bi-sindolylmaleimide I and/or inhibition of NHE1 with 100 microm amiloride abolished aldosterone vasoconstrictor action of resistance mesenteric arteries. We conclude that aldosterone-mediated increase in vascular tone is related to a nongenomic mechanism that involves protein kinase C, PI3-K, and NHE1 activity. Eplerenone is an effective blocker of nongenomic effects of aldosterone in vascular tissue.

Abstract-The aim of the present study was to demonstrate rapid effects of aldosterone on the Na ϩ -H ϩ exchanger in strips of human vascular vessels and to determine whether 11␤-hydroxysteroid dehydrogenase enzyme (11␤-HSD) could play a protective role in this response, such as that described for the classic type I mineralocorticoid receptor (MR). The activity of 11␤-HSD isoforms 1 and 2 were measured in fetal and adult arteries. Both isoforms are present in adult and fetal vessels. However, a significant difference in the proportion of each isoform was found. Isoform 1 activity (in pmol ⅐ min Ϫ1 ⅐ 100 mg Ϫ1 protein) was 42Ϯ5 in fetal vessels and 29Ϯ2 in adult arteries, and isoform 2 activity was 78Ϯ7 in fetal and 12Ϯ2 in adult tissue. The nongenomic effect of aldosterone on Na ϩ -H ϩ exchanger activity was measured in strips of chorionic and radial uterine arteries loaded with the pH-sensitive dye 2Ј,7Ј-bis(2-carboxyethyl)-5,6-carboxyfluorescein. Recordings of intracellular pH (pH i ) were made by videofluorescence microscopy. Aldosterone (0.5 nmol/L) rapidly increased pH i , with a half-maximal effect between 2 and 3 nmol/L in both fetal and adult vessels. Ethylisopropylamiloride, a specific inhibitor of the Na ϩ -H ϩ exchanger, inhibited this effect. The hormone-mediated increase in pH i was unaffected by spironolactone, a classic antagonist of MR, but was completely blocked by RU28318. Cortisol (up to 1 mol/L) had no effect on pH i , but when applied in the presence of carbenoxolone, a dramatic increase in Na ϩ -H ϩ exchanger activity was evident. The increments on pH i for each cortisol concentration were similar to those observed for aldosterone. These findings suggest that vascular 11␤-HSD plays an active role in maintaining the specificity of the rapid effects of aldosterone.

Background and objectives: Hemodialysis patients (HD) display high rates of cardiac diseases and mortality. In chronic kidney disease, vascular injury leads to coronary artery disease, heart failure, and stroke. Carotid intima-media thickness (CIMT) measurements are currently widely used in randomized controlled trials (RCTs) to study the efficacy of interventions. An RCT was designed for the assessment of the safety and effectiveness of spironolactone to inhibit the progression of CIMT in HD patients as a primary outcome. Secondary outcomes included measurements of plasma potassium.Design, setting, participants, & measurements: HD patients were randomly assigned to receive 50 mg spironolactone or placebo thrice weekly after dialysis. In between dialysis sessions, plasma potassium concentrations were measured every month. Ultrasonographic measurements of CIMT were done at the beginning of the study and after 2 years.Results: Fifty-three age-and sex-adjusted patients (30 with drug and 23 with placebo) successfully completed the trial. There were no significant differences between the two groups in all profiles studied at baseline. Measurements of CIMT after 2 years showed a progression in the placebo group, whereas in the spironolactone group a significant decrease or even reversed CIMT was observed. Progression rates (mm/yr) were: common carotid, placebo: 0.06 ؎ 0.07, spironolactone: 0.01 ؎ 0.04; carotid bifurcation, placebo: 0.15 ؎ 0.27, spironolactone: 0.0001 ؎ 0.01; internal carotid, placebo: 0.10 ؎ 0.12, spironolactone: ؊0.10 ؎ 0.15. No episodes of hyperkalemia were observed, but a slight increase in plasma potassium was found in the spironolactone group.Conclusions: Fifty milligrams of spironolactone thrice weekly significantly reduced the progression of CIMT in HD patients.

Abstract-Chronic renal failure causes left ventricular hypertrophy, but the molecular mechanisms involved remain unknown. We, therefore, investigated whether the mineralocorticoid receptor is implicated in the cardiac hypertrophy observed in uremic rats and whether mineralocorticoid receptor blockade could be protective in chronic renal failure. Experimental groups were: control rats, uremic rats (NPX) with 5/6 nephrectomy (5 weeks), and NPX rats fed with spironolactone for 5 weeks. Systolic blood pressure was increased in both NPX rats and NPX rats fed with spironolactone for 5 weeks. Echocardiography revealed concentric left ventricular hypertrophy in uremia, which was attenuated by spironolactone. Enlarged cardiomyocyte size was observed in both left and right ventricles of NPX rats, an effect that was prevented by spironolactone. Mineralocorticoid receptor antagonism attenuated the increase of ventricular brain natriuretic peptide mRNA levels induced by nephrectomy. Left ventricular gene expressions of aldosterone synthase, mineralocorticoid receptor, and hydroxysteroid dehydrogenase type 2 were the same in the 3 groups, whereas gene expression of the glucocorticoid receptor was significantly diminished in chronic renal failure rats. No significant differences in cardiac aldosterone were observed between control rats and NPX rats, although NPX rats fed with spironolactone for 5 weeks showed increased plasma aldosterone levels. However, a significant increase in serum and glucocorticoid-inducible kinase-1 mRNA expression and protein was present in the NPX group; spironolactone treatment significantly reduced serum and glucocorticoid-inducible kinase-1 mRNA and protein in the left ventricle. Uremic rats exhibited a significant increase of superoxide production and reduced nicotinamide-adenine dinucleotide phosphate oxidase subunits expression (NOX-2, NOX-4, and p47 phox ) in the left ventricle, which was prevented by the mineralocorticoid receptor antagonist. Our findings provide evidence of the beneficial effects of spironolactone in cardiac hypertrophy and cardiac oxidative stress in chronic renal failure. (Hypertension. 2008;52:295-300.) Key Words: aldosterone Ⅲ mineralocorticoid receptor Ⅲ cardiac hypertrophy Ⅲ SGK1 Ⅲ oxidative stress Ⅲ hydroxysteroid dehydrogenase type 2