Distribution of adrenocorticotrophic hormone-stimulated adenylate cyclase in the adrenal cortex.

Abstract

SUMMARY The intra-adrenal distribution of adenylate cyclase was measured in microsections of guinea-pig and rat adrenals. Addition of α-adrenocorticotrophin-(1–24)-tetracosapeptide (α1–24ACTH) in vitro to sections of normal guinea-pig adrenals stimulated enzyme activity in glomerular—fascicular border zone tissue and reticular tissue. The intravenous injection of α1–24ACTH increased adenylate cyclase activity in sections of adrenal cortex from dexamethasone-treated guinea-pigs. Enzyme activity was enhanced in glomerular—fascicular border zone tissue, reticular and fascicular—reticular border zone tissue. In the rat, hypophysectomy reduced adrenal adenylate cyclase activity to undetectable levels within 48 h. Addition of α1–24ACTH to tissue sections in vitro augmented enzyme activity. Adenylate cyclase activity was also measured in homogenates of whole guinea-pig adrenal tissue. α1–24ACTH (10, 100 and 1000 ng/ml) stimulated basal enzyme activity, whereas porcine insulin (400 pg/ml and 4 ng/ml) was without effect. Insulin inhibited the stimulation of adenylate cyclase activity by α1–24ACTH at concentrations of 10 ng/ml and 100 ng/ml. At higher concentrations of α1–24ACTH, insulin was without effect.