Regulation of cholesterol metabolism in rat adrenal glands: effect of adrenocorticotropin, cholesterol, and corticosteroids on acyl-coenzyme A synthetase and cholesterol ester hydrolases.

Abstract

The regulation of cholesterol metabolism in rat adrenal glands, especially the effect of ACTH, cholesterol, and corticosteroids on acyl-coenzyme A (CoA) synthetase and cholesterol ester hydrolases was investigated. A significant increase in acyl-CoA synthetase activity and decrease in cholesterol ester hydrolase activities were observed in 24-h hypophysectomized rats. Acute injection of ACTH, however, reversed these changes, whereas dexamethasone administration had no effect. When 4-aminopyrazolo[3,4-d]pyrimidine was given to rats, adrenal cholesterol ester content and the acyl-CoA synthetase activity declined and the activities of the cholesterol ester hydrolases were increased in association with the rise of plasma ACTH concentration. When dexamethasone, which suppresses ACTH secretion, was simultaneously administered with 4-aminopyrazolo[3,4-d]pyrimidine no changes except for a decrease in plasma cholesterol level occurred. In hyperlipidemic rats the acyl-CoA synthetase activity increased when a high cholesterol diet was given and the plasma cholesterol level was increased. These results suggest that acyl-CoA synthetase is under the influence of ACTH and also the plasma cholesterol concentration, and that cholesterol ester hydrolases are mainly regulated by ACTH.