In vitro Release of ACTH from Dispersed Rat Pars Intermedia Cells. I. Effect of Secretagogues

Abstract

Studies were made to test the responsiveness of dispersed pars intermedia (PI) cells to a number of secretagogues that are known to alter ACTH release from the pars distalis (PD) in vitro. Incubation in high [K+], which will increase ACTH release from the PD, did not alter ACTH release from the PI; a crude extract of rat hypothalamus (HE) increased ACTH release from PD and PI. The effect of HE was not due to its vasopressin content, since pretreatment of the extract with thioglycolic acid did not modify its ACTH-releasing activity and neither lysine nor arginine vasopressin stimulated ACTH release from the PI, and a partially purified CRF preparation, which will stimulate ACTH release from the PD, did not alter ACTH release from the PI. The hypothalamus may contain a substance(s) that will stimulate ACTH release from the PI and that the ''secretagogue'' is neither vasopressin nor the same CRF that will stimulate ACTH release from the PD.