Cyclobuta-dithymidine induction by solar-simulating UV radiation in human skin. I. Protection by constitutive pigmentation.

The induction and persistence of cyclobuta-dithymidine (T less than greater than T) photoproducts in human skin samples was measured following exposure to artificial solar radiation. DNA extracted from human epidermis, irradiated with the equivalent of 15 to 120 min of midday sunlight, was analyzed by enzyme-linked immunosorbent assay (ELISA). Heavily pigmented skin required 2- to 4-fold higher doses than non-pigmented skin to produce similar amounts of T less than greater than T photoproducts. These results demonstrate the effectiveness of constitutive epidermal pigmentation in protecting epidermal cell DNA from solar UV-induced damage.