Studies on the mechanism of action of the adrenocorticotropic hormone.

It has been demonstrated that adrenocorticotropic hormone (ACTH) stimulates isolated, perfused adrenal glands (1) and adrenocortical tissue slices (2, 3) to release increased quantities of corticosteroid hormones. These findings are in accord with the well established fact that ACTH in tivo causes the adrenal cortex to secrete increased quantities of the adrenal steroid hormones. The present work was performed in an attempt to learn more about the mechanism by which ACTH effects this stimulation of the adrenal cortex. The first group of experiments indicated that ACTH acts primarily by increasing the rate of corticosteroid synthesis rather than by primarily causing release of the steroid hormones. Further investigation of the mechanism of action of ACTH revealed that the adrenal stimulation is accompanied by an increase of phosphorylase activity in the tissue. Data will be presented showing the relationship between phosphorylase activity and steroidogenesis.