Effect of angiotensin converting enzyme inhibitor on serum aldosterone and potassium level.

An angiotensin converting enzyme inhibitory, captopril (or SQ 14225), was administered orally to 23 hypertensive patients under a constant sodium and potassium diet. It resulted in reduction of plasma aldosterone concentration which was related significantly to the increase of serum potassium level (r = -0.533), but only weakly to the reduction of plasma angiotensin II level (r = 0.474). Aldosterone level remained suppressed in the face of increased serum potassium. The effects on aldosterone level and potassium were greater in patients with high plasma renin activity than in those with low and normal plasma renin activities. They also paralleled the reduction in blood pressure. It is suggested that reduction in aldosterone level and potassium retention were caused by blockade of angiotensin II formation by captopril, but the potassium retention was additionally influenced by renal impairment.