[The effect of dopaminergic antagonists on plasma aldosterone in normal subjects and patients with hypopituitarism].

Although angiotensin II, ACTH and potassium are generally acknowledged as major factors in regulating the influences on aldosterone secretion, it has recently been reported that dopamine is a potent inhibitor of aldosterone secretion in man and animals. In the present study, we investigated the effect of two kinds of dopaminergic receptor antagonists, metoclopramide and sulpiride, on plasma aldosterone concentration (PAC) and serum prolactin (PRL) in man. Normotensive volunteers and patients with hypopituitarism were injected with metoclopramide (10 mg i.v.) or sulpiride (10 mg i.m.). In normal volunteers, metoclopramide increased both PAC and PRL levels, and showed a maximum level at 30 minutes after injection. In patients with hypopituitarism, PAC tended to increase without change of PRL, which suggested that the increase in PAC by metoclopramide might have a direct inhibitory effect on the dopaminergic receptor in the adrenal gland. Moreover another antagonist, sulpiride also increased PRL but contrary tended to decrease PAC. These results suggested that PRL responses to both inhibitors were mediated by dopaminergic antagonist activity at the level of pituitary receptors. However dopamine-induced modulation of aldosterone secretion may be different from that of PRL at dopaminergic receptors. These results suggested that modulatory inhibition of aldosterone secretion by dopamine may be affected by difference of affinity of dopamine to receptor as organ specificity, or different affinity of metoclopramide and sulpiride to adrenal dopamine receptor.(ABSTRACT TRUNCATED AT 250 WORDS)