Dopamine selectively inhibits aldosterone responses to angiotensin II in man

Previous studies have demonstrated that dopamine inhibits the aldosterone response to angiotensin II in the sodium deplete state in man, but not in the normal sodium balance state. In this study we investigated nine normal male volunteers in balance at 10 mEq sodium intake to determine whether the inhibitory effect of dopamine is selective for angiotensin II-induced aldosterone secretion or also inhibits ACTH-induced stimulation of aldosterone secretion. After 2 h dopamine infusion, angiotensin II was administered in cumulative doses of 0.5, 1, 2, 4 and 6 pmol/kg/min, each dose for 30 min. Aldosterone responses to angiotensin II were greater with vehicle than with dopamine at doses of 2, 4 and 6 pmol/kg/min (P less than 0.05). The slope of the angiotensin II-aldosterone dose-response curve was steeper with vehicle (0.46) than with dopamine (0.26) (P less than 0.05). However, when ACTH in doses of 0.5, 1, 2 and 5 U/h was substituted for angiotensin II, aldosterone responses were similar with vehicle and dopamine, as were the dose-response slopes. Thus, dopamine inhibits angiotensin II- but not ACTH-induced aldosterone secretion in sodium deficient man.