Effect of combined administration of dexamethasone and captopril on plasma aldosterone response to angiotensin II in normal man.

Aldosterone responses to angiotensin II were evaluated in normal subjects in 3 conditions, (1) with suppression of neither ACTH secretion nor angiotensin II, (2) with suppression of ACTH by dexamethasone, and (3) with suppression of both ACTH and angiotensin II by combined administration of dexamethasone and captopril. Baseline levels of plasma aldosterone were significantly lowered by administration of either dexamethasone or both dexamethasone and captopril. Aldosterone responsiveness to angiotensin-II was not altered by suppression of ACTH secretion. However, the responsiveness was significantly enhanced during suppression of both ACTH and angiotensin II. These results suggest that aldosterone response to angiotensin II in normal man is not dependent upon endogenous ACTH secretion, but to an action of angiotensin II on the pituitary gland to release ACTH. The combined administration of dexamethasone and captopril may be a useful maneuver to assess more precisely the reactivity of the adrenal cortex to angiotensin II in man.