Effects of angiotensin III and ACTH on aldosterone secretion

ACTH and des-Asp1-angiotensin II (AIII) can raise plasma aldosterone. To assess the threshold for ACTH and AIII stimulated adrenal steroidogenesis we infused ACTH (from 0.03 to 10 ng ACTH/min) and AIII (from 0.1 to 20 ng/kg/min) to dexamethasone pretreated sodium deplete normal subjects and patients with primary aldosteronism, chronic renal failure, and end stage renal disease maintained with continuous ambulatory peritoneal dialysis. Plasma aldosterone in the primary aldosteronism group increased significantly at 0.3 ng ACTH/min compared with 1 to 3 ng ACTH/min in all other groups. The threshold dose for an ACTH stimulated rise in plasma aldosterone was as at least as low as the dose necessary to raise cortisol in all groups. The threshold dose for an AIII stimulated rise in plasma aldosterone was 4 ng/kg/min in normals and between 1 and 3 ng/kg/min in primary aldosteronism. The metabolic clearance rate (MCR) of aldosterone was determined by constant infusion of [3H]-aldosterone. The decline in MCR during AIII infusion contributed less than 15% to the rise in plasma aldosterone in normals and patients with primary aldosteronism.