In vitro temporal cAMP and cortisol responses to ACTH by the normal human adrenal gland

The in vitro temporal cAMP and cortisol responses of normal human adrenocortical tissue to ACTH were evaluated. ACTH stimulated rapid increased in cAMP levels and cortisol output, however, significantly increased cAMP levels preceded output only at the higher ACTH doses studied. Cortisol output plateaued with ACTH (10--100 MIU/ml) while cAMP levels continued to increase. The findings indicate that the unitary role of cAMP as the second messenger of ACTH action in the human adrenal cannot be assumed from data derived from lower forms and that the mechanism of action of ACTH in the human may be modulated by additional factors.