ANGIOTENSIN II AND K CHALLENGE FOLLOWING PROLONGED ACTH ADMINISTRATION TO NORMAL SUBJECTS

Abstract

Healthy male volunteers (12) on a normal Na and K intake and ambulatory received ACTH (40 IU, i.m.) twice daily for 5 days followed by 2 days of angiotensin II (5-13 ng/kg body wt per min for 60 min) or oral potassium citrate (30 meq/h .times. 3). A discordance in the aldosterone-stimulating and pressor responses of angiotensin II was unmasked with only the latter response being positive following ACTH-induced refractoriness. K loading was a much more potent natriuretic stimulus than angiotensin II treatment. K selectively enhanced aldosterone secretion by overcoming the inhibition in secretion of the mineralocorticoid induced by prolonged ACTH exposure.