Tonic Dopaminergic Suppression of Plasma Aldosterone*

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Abstract
To investigate the interaction between dopamine and aldosterone in man, either the dopamine antagonist, metoclopramide [methoxy-2-chloro-5-procainamide (M)], or a placebo was given by an i.v. bolus in a random, double blind fashion to 9 supine volunteers on a hospital diet (mean urinary Na excretion, 135 .+-. 17 vs. 145 .+-. 26 meq[equivalents]/24 h; P = not significant). After M (10 mg), plasma aldosterone (PA) rose from 6.4 .+-. 1.1 to 14.0 .+-. 2.2 (standard error of the mean) ng/dl (P < 0.01) within 15 min. Plasma renin activity, K and cortisol were unchanged. PRL [prolactin] increased 10-fold, but individual increments in PA and PRL did not correlate significantly. Oral M (10 mg) produced a rise in PA in only 2 of 5 volunteers. To determine whether the increase in PA was due to the dopamine antagonist properties of M, the i.v. study was repeated in 4 of the volunteers during an ongoing dopamine infusion. The integrated incremental change in PA during the hour after M administration was markedly blunted (399 .+-. 56 vs. 69 .+-. 32 ng/dl per min; P < 0.05), and the PRL response was totally abolished. Assuming no major effects of M on the metabolic clearance rate of adlosterone, these data suggest a tonic inhibitory influence of dopamine on aldosterone secretion.

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