Isolated adrenal cortex cells: ACTH4-23 (NH2), ACTH5-24, ACTH6-24 and ACTH7-23 (NH2); cyclic AMP and corticosterone production.

Abstract

SummarySuspensions of isolated adrenal cortex cells of the rat respond to the addition of ACTH1-24 and related peptides with production of cAMP and corticosterone. A concentration of ACTH1-24 which results in less than 20% of maximum cAMP production induces near-maximum corticosterone production; a concentration which results in 1-3% cAMP production induces 50% of maximum corticosterone production. ACTH4-23(NH2) and ACTH5-24 are less potent than AC TH1-24, but induce the same maximum corticosterone production (Bmax) as ACTH1-24; ACTH6-24 induces a maximum equal to 0.4 of Bmax; ACTH7-23(NH2) is inactive. AC TH4-23(NH2), ACTH5-24 and ACTH6-24 induce 0.86, 0.45 and 0.01 of the maximum cAMP production characteristic of AC TH1-24; respectively; ACTH7-23(NH2) is inactive. ACTH7-23(NH2) is a competitive antagonist and shifts the ACTH1-24 log concentration curves for cyclic AMP and for corticostemne to the same degree. These observations are discussed in terms of a dual receptor model and in terms of a single sit...