Erythrocyte Na +, K + pump inhibition after saline infusion in essentially hypertensive subjects: effects of canrenone administration

Abstract

The effects of a 2-litre isotonic saline infusion, with and without prior oral canrenone (150 mg) administration, on erythrocyte Na +, K + pump, urinary sodium excretion and arterial pressure were evaluated in nine patients with essential hypertension. Ouabain-sensitive Na + efflux in fresh erythrocytes was used as an index of Na +, K + pump activity, and the inhibitory effect on this ion efflux of preincubation of erythrocytes in plasma was used to test the presence of a circulating ouabain-like substance. Erythrocyte Na +, K + pump activity decreased significantly ( P < 0.01) after saline infusion; canrenone administration was able to prevent this inhibition. Plasma from hypertensive patients obtained before saline infusion significantly ( P < 0.01) inhibited the Na +, K + pump of erythrocytes from normal subjects, while plasma taken after the saline infusion plus canrenone was unable to produce any significant inhibition. Both systolic and diastolic arterial pressure fell significantly ( P < 0.05) only at the end of saline infusion with prior canrenone administration. This study supports the hypothesis that protection of Na +, K + pump against endogenous inhibitors, other than exogenous, seems to be a pharmacological effect of canrenone, and may partly explain its antihypertensive activity.