DETECTION OF ACTIVE UV-PHOTOPRODUCT REPAIR IN MONKEY SKIN IN-VIVO BY QUANTITATIVE IMMUNOHISTOCHEMISTRY

Ultraviolet-induced cyclobutane pyrimidine dimers (CPDs) and pyrimidin e-pyrimidone (6-4)photoproducts in DNA were quantitatively measured in monkey skin using an immunohistochemical method with two specific mon oclonal antibodies. The skins of Cynomolgus monkeys (Macaca fascicular is) were irradiated with UV light and processed for preparation of con ventional formalin-fixed, paraffin-embedded histological sections. Bot h of the photoproducts were detectable in the nuclei of epidermal cell s at doses of 500 J/m(2) for UVB and 50 J/m(2) for WC, respectively, n uclear staining being clearly dose-dependent. Time course studies also showed a statistically significant decrease in nuclear staining with time after exposure to either UVB or UVC irradiation. Although only 30 % of CPDs were removed from DNA in the first 24 h, about half of the ( 6-4) photoproducts were repaired within 3 h post-UV irradiation. Stain ing completely disappeared by 48 h in the (6-4) photoproduct case and by 72 h in the case of CPDs. The results suggest that epidermal cells of monkey skin can efficiently repair UV-photoproducts in DNA, but tha t the capacity is slightly less than in man.