Effects of metoclopramide, a dopamine antagonist, on secretion of aldosterone and renin release in patients with primary aldosteronism

To assess the interaction between dopamine and aldosterone secretion in primary aldosteronism, the dopamine antagonist, metoclopramide (methoxy-2-chloro-5-procainamide), was given as an i.v. bolus (10 mg) to 5 patients with primary aldosteronism and 5 normal subjects treated with dexamethasone (2 mg/day) to eliminate an influence of ACTH. Metoclopramide increased plasma aldosterone concentration (PAC) in primary aldosteronism from 39.1 +/- 15.5 to 42.5 +/- 15.9 ng/100 ml (p less than 0.05) and also from 12.9 +/- 2.3 to 23.6 +/- 3.4 ng/100 ml (p less than 0.01) in normal subjects at 15 min. Plasma renin activity (PRA), and plasma concentrations of cortisol, potassium, and sodium did not significantly change with metoclopramide in either primary aldosteronism or normal subjects. Plasma prolactin increased by 12- and 20-fold in primary aldosteronism and in normal subjects, respectively, but there was no significant positive correlation between changes in PAC and in plasma prolactin in either primary aldosteronism or normal subjects. It is suggested that dopamine inhibits the secretion of aldosterone in primary aldosteronism as well as in normal subjects. It seems unlikely that dopamine affects the release of renin in primary aldosteronism.