ANGIOTENSIN II STIMULATES THE RELEASE OF ACTH FROM DISPERSED RAT ANTERIOR PITUITARY CELLS

Abstract

In a rat anterior pituitary dispersed cell system, angiotensin II stimulated the release of ACTH at concentrations ranging from 100 pmol/l to 1 .mu.mol/l, with a maximal response being given by 10 nmol/l. The angiotensin II antagonist, saralasin, was able to block completely at a concentration of 1 .mu.mol/l the stimulation of ACTH induced by 10 nmol/l angiotensin II, but had no effect on the basal release. The log dose-response curve for ACTH release by angiotensin II was shifted to the right in a parallel fashion by saralasin 10 nmol/l, suggesting competitive antagonism. The stimulation of ACTH release by a rat stalk-median eminence extract or by arginine vasopressin was unaffected by saralasin. Rat corticotrophs apparently contain angiotensin II receptors, and these may be involved in ACTH release in response to hypovolemic stress.