Cell membrane cation transport systems during aldosterone antagonism

Increased microparticle production and impaired microvascular endothelial function in aldosterone-salt-treated rats: protective effects of polyphenols

We aimed to characterize circulating microparticles in association with arterial stiffness, inflammation and endothelial dysfunction in aldosterone-salt-induced hypertension in rats and to investigate the preventive effects of red wine polyphenols. Uninephrectomized male Sprague-Dawley rats were treated with aldosterone-salt (1 µg.h⁻¹), with or without administration of either red wine polyphenols, Provinols™ (20 mg.kg⁻¹.day⁻¹), or spironolactone (30 mg.kg⁻¹.day⁻¹) for 4 weeks. Microparticles, arterial stiffness, nitric oxide (NO) spin trapping, and mesenteric arterial function were measured. Aldosterone-salt rats showed increased microparticle levels, including those originating from platelets, endothelium and erythrocytes. Hypertension resulted in enhanced aortic stiffness accompanied by increased circulating and aortic NO levels and an upregulation of aortic inducible NO-synthase, NFκB, superoxide anions and nitrotyrosine. Flow-induced dilatation was reduced in mesenteric arteries. These effects were prevented by spironolactone. Provinols™ did not reduce arterial stiffness or systolic hypertension but had effects similar to those of spironolactone on endothelial function assessed by flow-mediated vasodilatation, microparticle generation, aortic NO levels and oxidative stress and apoptosis in the vessel wall. Neither the contractile response nor endothelium-dependent relaxation in mesenteric arteries differed between groups. The in vivo effects of Provinols™ were not mediated by mineralocorticoid receptors or changes in shear stress. In conclusion, vascular remodelling and endothelial dysfunction in aldosterone-salt-mediated hypertension are associated with increased circulating microparticles. Polyphenols prevent the enhanced release of microparticles, macrovascular inflammation and oxidative stress, and microvascular endothelial dysfunction independently of blood pressure, shear stress and mineralocorticoid receptor activation in a model of hyperaldosteronism.

Effect of canrenone on the digitalis site of Na+/K(+)-ATPase in human placental membranes and in erythrocytes

It has been reported that canrenone, which is used in hypertensive therapy as an antialdosteronic drug, may also act as a blocker of ouabain effects. Several studies suggest that human plasma contains an endogenous ouabain-like factor similar to ouabain, which may be increased in hypertension, in pregnancy, and in the neonatal state. This study evaluated (1) the effect of canrenone on Na+/K(+)-ATPase in relation to ouabain in human placental membranes and erythrocytes by 3H-ouabain binding assay; (2) the capacity of canrenone (10 microM) to reverse the inhibition of Na+/K(+)-ATPase by ouabain and by ouabain-like factor (from umbilical cord plasma) in human erythrocytes employing a 86Rb uptake assay. Increasing concentrations of canrenone (0-350 microM) partially competed with 3H-ouabain binding in placental membrane (40%) and erythrocytes (60%). Scatchard plot from radioreceptor assay in placental membrane showed that ouabain and canrenone compete for the same binding site. In erythrocytes, canrenone completely reversed the inhibition caused by ouabain (5 x 10(-9) M) and ouabain-like factor (2 x 10(-9) M ouabain equivalents). A reduction of inhibition of about 50% was observed with ouabain and ouabain-like factor respectively at a concentration of 5 x 10(-8) M and 2 x 10(-8) M (ouabain equivalents). Our results thus provide evidence that canrenone, at therapeutical concentrations, is a partial competitive agonist of ouabain and of ouabain-like factor in human placental membranes and erythrocytes.