Melanocyte mitosis in UVB-irradiated mouse skin.

Little is known about the mitotic activity of the epidermal melanocyte population. Vincristine sulphate has now been used in vivo to study the frequency of mitosis of epedermal melanocytes in the ear skin of C57BL mice. It is shown that there is continuous formation of new melanocytes in unstimulated skin due to mitosis of pigment-producing epidermal melanocytes. The increase in this mitotic rate following daily UVB irradiation suggests that this is a major mechanism responsible for the UV-induced increase in the epidermal melanocyte population.