Toxic effect of ultraviolet light on melanocytes: use of animal models in pigment research.

Quantitative histologic investigations on the effect of UV radiation on mammalian melanocytes have shown similarities in the response to carcinogenic chemicals, UV radiation, and 8-methoxypsoralen combined with UV radiation. With all three regimens the melanocyte number increased in mice, whereas long-wavelength UV radiation alone did not change the numerical distribution of these cells. Although it is too early to say that similarity in response of these agents indicates identity in harmful effects of these agents, great care should be exercised in the application of psoralens to human skin in a combined treatment with UV radiation.