EFFECT OF ACTH ON VIP AND GALANIN RELEASE FROM THE PITUITARY

The effect of adrenocorticotropin (ACTH) on the release of four regulatory peptides from the anterior pituitary of male rats has been studied using an in vitro perfusion system. Quartered anterior pituitaries from male adult Wistar rats were perfused with buffer containing different concentrations of ACTH and, subsequently, 56 mM KCl. Fractions of 1.5 ml were collected at 3 min intervals and analyzed for vasoactive intestinal peptide (VIP), galanin, 7B2, and substance P, using specific radioimmunoassays. Concentrations of 0.02, 0.1, 0.2, and 0.4 nM ACTH produced increases of 117 ± 50%, 155 ± 90%, 163 ± 14%, and 161 ± 3% (mean + SE), respectively, of basal release of VIP (P < 0.001). However, concentrations of 1 µM and 2 µM ACTH suppressed VIP release to 74 ± 6% and 47 ± 4%, respectively, compared to basal release (P < 0.001). Results for galanin release were similar: Concentrations of 0.02, 0.1, 0.2, and 0.4 µM ACTH increased galanin release to 129 ± 4%, 136 ± 8%, 143 ± 9%, and 133 ± 9% of basal release (P < 0.001), and 1 and 2 µM ACTH provoked a suppression of 52 ± 7% and 50 ± 13%, respectively, compared with basal release (P < 0.001). Doses of ACTH that altered the secretion of VIP and galanin had no effect on 7B2 and substance P release. These results demonstrate that ACTH causes a release of pituitary VIP and galanin in vitro and, moreover, that this is a biphasic phenomenon. © 1990 by The Endocrine Society.