Nle4DPhe7α-Melanocyte-Stimulating Hormone Increases the Eumelanin:Phaeomelanin Ratio in Cultured Human Melanocytes

In mammals, melanin exists in two chemically distinct forms: the red-yellow phaeomelanin and the brown-black eumelanin. Although administration of the pigmentary hormone α-melanocyte-stimulating hormone (αMSH) and its synthetic analogue Nle4DPhe7αMSH induces skin darkening in man, the increases in melanogenesis in cultured human melanocytes in response to these peptides are relatively small, However, it is possible that MSH affects the eumelanin:phaeomelanin ratio rather titan total cellular melanin. Thus, this study examined the specific effects of Nle4DPhe7αMSH on the two melanins in cultured human melanocytes, quantifying eumelanin and phaeomelanin by hign performance liquid chromatography. Nle4DPhe7αMSH induced significant increases in the eumelanin content of these cells while having lesser and varied effects on the levels of phaeomelanin. As a consequences the eumelanin: phaeomelanin ratio was increased in every culture. These results demonstrate that Nle4DPhe7αMSH affects melanin type in human melanocytes and suggest a possible mechanism by which this peptide induces skin darkening in man