CULTURED HUMAN MELANOCYTES FROM BLACK-AND-WHITE DONORS HAVE DIFFERENT SUNLIGHT AND ULTRAVIOLET-A RADIATION SENSITIVITIES

Short-term and long-term survival of cultured neonatal foreskin melanocytes from black and white individuals were assessed following a single exposure to simulated sunlight or ultraviolet A (UVA) radiation. Melanocytes from black individuals contained significantly more melanin than melanocytes from white individuals (p < 0.05). Black and white melanocytes had similar survival profiles following simulated sunlight exposure, whereas black melanocytes were significantly more resistant to UVA cytotoxicity than melanocytes from white subjects (p < 0.05) at UVA dose's above 15 J/cm2. There was no difference in unscheduled DNA synthesis in the black or white melanocytes following simulated sunlight exposure and no unscheduled DNA synthesis was measurable following melanocyte exposure to UVA radiation. Low-dose UVA (1 or 5 J/cm2) was mitogenic to both black and white melanocytes. By analysis of co-variance, the melanin content of melanocytes of black and white subjects was significantly (p < 0.05) associated with susceptibility to UVA killing; melanocytes with high melanin content had high resistance to UVA cytotoxicity and those with low melanin content had low resistance to UVA cytotoxicity. From these data we suggest that the higher melanin content of melanocytes of black-subjects confers increased resistance to UVA damage. This is likely to be of importance in epidermal photodamage.