9-Isoleucine]ACTH 1–24, a competitive antagonist of ACTH 1–24 induced cyclic AMP and corticosterone production

Abstract

Substitution of tryptophan 9 in ACTH 1–24 by isoleucine results in complete loss of biological activity. A dose of 3.4 × 10 −5 M per ml fails to stimulate corticosterone and cyclic AMP production. This analogue inhibits cyclic AMP production and corticosterone production induced by ACTH 1–24 in isolated adrenal cortex cells. The I 50 values for corticosterone and cyclic AMP inhibition are 2.3 × 10 −6 M and 3.4 × 10 −6 M respectively.