Regional differences in the distribution of melanocyte-containing hair bulbs in the skin of male albino rats

by Nayuki Numata, Aisa Ozawa, Motoharu Sakaue

Hair gets its color from melanin produced by melanocytes in the hair matrix. The coloration patterns observed in most terrestrial mammals arise from the diverse color combinations within their fur, which depends on the distribution pattern of melanocyte-containing hair follicles. Albino rats genetically produce no melanin and their coats are thus white, but we speculated that melanocytes differentiate and localize within these rats’ hair matrix. We conducted a reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, which revealed both the mRNA expressions of two melanocyte markers (dopachrome tautomerase and tyrosinase) in skin of male albino (SD, Wistar, and F344) rats and the differences in the markers’ expression levels among skin areas. Immunohistochemistry using anti-Dct antibody demonstrated that immunopositive cells, i.e., melanocytes, were localized in the rats’ hair matrix, and that melanocytes containing hair bulbs were distributed in head, dorsal thorax, and dorsal midline areas, which is similar to hooded rats. Our results suggest that differences in the melanocyte presence among the skin regions should be considered when the results of gene expression analyses of albino rat skin are interpreted.