Cyclobuta-dithymidine induction by solar-simulating UV radiation in human skin: II. Individual responses

The purpose of this study was to examine cyclobuta-dithymidine (T*T) photoproduct induction and persistence in human skin exposed in situ to simulated solar UV radiation. Small areas of untanned skin in nineteen individuals were exposed using a solar UV apparatus that simulates both the spectrum and intensity of the UV portion of summer midday sunlight at 39 degrees N latitude. The equivalent of approximately 60 min of sunlight exposure (72KJ/m2) was administered, and T*T photoproducts were quantitated by enzyme-linked immunosorbent assay (ELISA) of DNA extracted from skin punch biopsies. Net yields of T*T photoproducts were determined in 10 individuals, with the majority (7 of 10) between 0.02 and 0.12 T*T per kilobase (Kb). The three remaining individuals had higher levels of photoproducts but were not unusually sensitive to solar UV as determined by minimal erythema dose (MED). Percentage loss of T*T photoproducts 4 h after exposure was determined in nine individuals to be 80.2 +/- 14.0%.