The eumelanin and pheomelanin contents in dorsal hairs of female recessive yellow mice are greater than in male

Abstract

The murine recessive yellow (Mc1r(e)) is a loss-of-function mutation in the receptor for alpha-melanocyte-stimulating hormone (MSH), melanocortin receptor 1 (MC1R), and produces yellow coats by inducing pheomelanin synthesis in hair follicular melanocytes. It is not known whether the Mc1r(e) mutation affects pheomelanin synthesis in other skin sites. In this study, the eumelanin and pheomelanin contents in the epidermis and dermis as well as hairs of wild-type and mutant mice were measured. The content of melanin was measured by high performance liquid chromatography. The eumelanin contents in the epidermis and dermis of newborn wild-type (Mc1r(+)/Mc1r(+)) mice (0.5, 3.5, 5.5, and 7.5 days) were much greater than those of mutant (Mc1r(e)/Mc1r(e)) mice, whereas the pheomelanin contents in the epidermis and dermis of mutant mice were much greater than those of wild-type mice. No sex differences in the contents of eumelanin and pheomalanin in the epidermis and dermis both in mutant and wild-type mice were observed. The eumelanin contents in mutant hairs (5-week-old) was much smaller than in wild-type hairs, whereas the pheomelanin contents in mutant hairs was much greater than in wild-type hairs. However, the eumelanin and pheomelanin contents in mutant female hairs were greater than in male. These sex differences were not observed in wild-type mice. The Mc1r(e) gene stimulates pheomelanin synthesis in the epidermis, dermis and hair follicles. In addition, eumelanin and pheomelanin contents in Mc1r(e)/Mc1r(e) hairs may be influenced by the sex difference.