COAT COLOR DARKENING IN A DOG IN RESPONSE TO A POTENT MELANOTROPIC PEPTIDE

Analogues of a melanocyte-stimulating hormone (alpha-MSH) have been do cumented to be effective in inducing integumental melanogenesis in sev eral species. These melanotropin analogues are more potent than the na tural hormone and have prolonged biological activity, without apparent teratogenic or other toxic effects, at least in rodents. In a pilot s tudy, a cyclic alpha-MSH analogue, Ac-[Nle(4), Asp(5), ($) under bar D -Phe(7), Lys(10)] alpha-MSH(4-10)-NH2, was administered SC to a dog at a dose of 1 mg of analogue in 1 ml of 0.9% NaCl for 3 weeks, without noticeable adverse effects. There was gradual and extensive darkening of the coat, which originally was predominantly tan, with tips of blac k. Initially, the darkening involved face and extremities, then gradua lly expanded to include the trunk and tail hair. Visual pigmentation p eaked approximately 2 months after injections were completed, As new h air growth continued subsequent to the injections, the original tan co lor appeared at the proximal end of the hair shaft, leaving a dark ter minal band on all affected hairs. These observations clearly indicated that follicular melanogenesis can be induced in dogs by treatment wit h a melanotropic peptide.