THE PRESENCE OF TYROSINASE AND RELATED PROTEINS IN HUMAN EPIDERMIS AND THEIR RELATIONSHIP TO MELANIN TYPE

The present study was carried out to investigate the abundance of tyro sinase and related proteins (TRP-1 and TRP-2) in human epidermis and t heir relationship to melanin type. Positive immunocytochemical stainin g was seen for all three proteins in epidermal melanocytes. For each p rotein the numbers of positively stained melanocytes were similar in a ll subjects studied irrespective of skin type. Following 5 daily suber ythemal doses of UVB the melanocytes were larger, more dendritic, and increased in number. With TRP-1 and TRP-2 the increase in number in re sponse to UVB was unrelated to skin type and, hence, with melanin type but with tyrosinase there was a much greater increase in skin types I II and IV than in skin type I and II. The enhanced numbers of tyrosina se-positive melanocytes were accompanied by increased staining intensi ty, suggesting a greater expression of tyrosinase in the melanocytes f rom skin types III and IV compared with skin types I and II. This incr ease in tyrosinase could be related to the greater levels of eumelanin found in skin types III and IV, and this is in keeping with the view that higher levels of tyrosinase are associated with the production of eumelanin than phaeomelanin.