The MSH-like activity of pineal hormone E5 in vivo and in vitro experiment.

Further experiments have revealed that the polypeptidic hormone E5 has a MSK-like effect, as experimentally demonstrated on the frog skin. In Rana esculenta, 30-120 min after a subcutaneous injection of 0.2 mg purified E5B or E5P/100 g b.w., the skin blackened and the effect lasted for about two hours. A comparable effect was induced by incubating the fragment of frog abdominal skin with a similar solution of E5. This MSK-like effect appears to be identical upon mammalian melanocytes in C57/B16 mice strain valves in vitro experiment. The results obtained indicate that pineal gland can influence melanocyte activity directly and suggest the possible implication in such pathological conditions as melanomas, vitiligo, etc.