Isolated Adrenal Cells: The Partial Agonists [Trp(Nps)9]ACTH1-39 and [Trp(Nps)9]ACTH1-24 (Nitrophenyl Sulfenyl Derivatives of ACTH)

The o-nitrophenyl sulfenyl derivatives of ACTH1-39 and ACTH1-24 are partial agonists. They stimulate corticosterone production when added to suspensions of isolated adrenal cells. Maximum rate of steroidogenesis induced by these derivatives is less than that induced by the agonists ACTH1-39 and ACTH1-24. In appropriate doses the derivatives antagonize the steroidogenic action of the agonists. These observations emphasize the importance of tryptophan at position 9 of the ACTH molecule in the process involved in excitation of receptor.