The involvement of melanotrophins in physiological colour change in the dogfish Scyliorhinus canicula

Abstract

Desacetylated α-, β-, and γ-MSH purified from the neurointermediate lobe of the pituitary gland of the dogfish Squalus acanthias were all equipotent in turning partially hypophysectomized dogfish, Scyliorhinus canicula, dark. However, each possessed less than 2% of the melanotrophic activity of either acetylated mammalian α-MSH or synthetic acetylated Squ. acanthias α-MSH. These results suggest that acetylation is much more important than amidation in determining melanotrophic potency in vivo in the dogfish. Intravenous administration into grey-adapted dogfish of an antibody capable of binding the α-MSH-like peptides present in the blood was very effective at inducing pallor. In contrast, a γ-MSH antibody had no effect on the melanophores of Scy. canicula. Overall the results suggest that it is α-melanotrophins that regulate physiological colour change in the dogfish Scy. canicula.