Influence of cholecystokinin on hypothalamic-stalk median-eminence-extract stimulation of ACTH output from isolated pituitary cells.

The influence of cholecystokinin 33 (CCK33) on CRF-like stimulation of ACTH output was tested in vitro using isolated pituitary cells. ACTH was assayed using isolated adrenal cell preparations. The CRF-like material was contained in a crude acetic-acid extract of hypothalamic stalk median eminence (HSME). CCK33, in doses of 1 U, 10(-3) U, and 10(-6) U/ml cell suspension had no influence on basal or ACTH-stimulated corticosterone output from isolated adrenal cells. Isolated pituitary cells responded in a dose-related fashion of HSME extract, however, the absolute response to a given dose of HSME extract varied according to the basal (non-stimulated) output of a particular cell preparation. CCK33, in the dose range tested, had no influence on basal ACTH output. In contrast, 10(-3) U/ml oc CCK33, which corresponds to a concentration of 8 X 10(-11) M, significantly inhibited the output of ACTH from isolated pituitary cells stimulated by 0.2 equivalents of HSME. Higher concentrations of CCK33 had a variable effect. We conclude that cholecystokinin may have a role in the regulation of HSME-stimulated ACTH output from the pituitary.