Chromatographic and electrophoretic characterization of melanocyte-stimulating substances in the duck pituitary

Peptides with melanotrophic activity in the duck pituitary were resolved using chromatography in Bio-Gel P-6. Four distinct peaks of activity were obtained. Three of them coincided roughly with synthetic ACTH 1–39, pure beef β-MSH, and synthetic α-MSH. The latter accounted for most of the melanotrophic potency of the duck pituitary. α- and β-MSH-like fractions were further purified by electrophoresis in cellulose acetate strips. Only the former fraction yielded a major band which coincided again with α-MSH, whereas the other fraction was resolved into several bands with melanophoric activity, with a minor one coinciding with β-MSH. It is concluded that the bulk of melanotrophic activity of the duck pituitary corresponds to a peptide which behaves as α-MSH in the analytical systems used.