Role of estradiol and 2-hydroxyestradiol in melanin formation in vitro

Melanin formation from 3,4-dihydroxyphenylalanine (dopa) was studied in the presence of estradiol and 2-hydroxyestradiol by use of a tyrosinase isolated from B16-F10 melanoma cells grown in C57 black female mice. Both steroids were found incorporated into melanin, but the 2-hydroxy compound was incorporated to a higher extent. The melanin was also able to bind substantial amounts of the two steroids, and the more highly oxidized compound showed higher binding. Melanin isolated from incubates of dopa with mushroom tyrosinase has the ability to bind the steroids and to incorporate small amounts into its structure. It is suggested that melanin in mammalian tissues may function as a depository for estrogens, particularly for those which are more highly oxidized.