MELANIN-CONCENTRATING HORMONE GENE-RELATED PEPTIDE STIMULATES ACTH, BUT NOT ALPHA-MSH, RELEASE FROM THE TILAPIA PITUITARY

Tilapia (Oreochromis mossambicus; teleostei) melanin-concentrating hor mone gene-related peptide (tMgrp) was tested for tropic actions on ade nocorticotropin hormone (ACTH) and alpha-melanocyte stimulating hormon e (alpha-MSH) producing cells in the tilapia pituitary gland in vitro. Up to 100 mu M synthetic tilapia Mgrp (tMgrp) had no effect on alpha- MSH release from tilapia neurointermediate lobes in a superfusion set up. However, at concentrations above 1 mu M, tMgrp concentration depen dently stimulated ACTH release from tilapia anterior lobes. This is th e first evidence that Mgrp modulates ACTH release from teleost cortico tropes, and this might implicate the peptide in the regulation of the pituitary-interrenal axis of fish.