Effects of adrenocorticotropic hormone on rat adrenal corticosteroidogenesis in vivo.

The effect of ACTH on cortico-steroid biogenesis from cholesterol by rat adrenal glands in vivo has been studied. 1. Rapid synthesis and secretion of radioactive corticosterone by the rat adrenal was observed after “retrograde” infusion of cholesterol-7α-3H through the adrenal vein. There were no significant differences in formation of radioactive cor-ticosterone between control, hypophysectomized and ACTH-treated groups, suggesting that cor-ticosterone is formed rapidly from circulating cholesterol and secreted instantaneously and that this conversion is maintained to some extent in the absence of ACTH. 2. The effect of ACTH on radioactive cortico-sterone production by adrenals of rats in which the adrenal cholesterol had been labeled by intravenous administration of cholesterol-7α-3H 24 hr earlier has been observed. The specific activities of corticosterone from control and ACTH-treated groups were lower than those from adrenals of hypophysectomized animals. These results support the suggestion that the...