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Identification of DNA adducts in peripheral lymphocytes could serve as a means of monitoring human exposure to potential genotoxic agents. In this study, DNA from peripheral lymphocytes of smokers and nonsmokers was examined for adducts by the P1 nuclease P-postlabeling technique. Thin layer chromatography (TLC) maps from both groups revealed multiple DNA adducts which ranged from no adducts for one individual to six adducts for a different individual. The total DNA adduct concentrations were approximately one adduct in 10- 10 normal nucleotides. Comparison of the adduct TLC profiles revealed individual variation in both pattern and level of DNA adducts. The type and amount of adduct was not influenced by smoking history and remained unchanged in four out of six subjects who were resampled after a 1 month interval. The capacity of lymphocytes to form BaP-derived DNA adducts after a 72 h incubation with 10 M [H]BaP was measured by both high-performance liquid chromatography (HPLC) and P-postlabeling analysis. The adduct values detected by [H]nucleoside concentrations on HPLC ranged from 1 to 7 fmol adduct per μg DNA (3.3–23.3 adducts per 10 nucleotides). The[H] nucleoside values were consistent with values obtained by P-postlabeling of the same sample (correlation coefficient of 0.88). No relationship was apparent between the capacity of lymphocytes to form a [H] BaP- derived adduct and the concentration of any adduct, or total adducts present in untreated lymphocytes. These results suggest that multiple DNA adducts are present in lymphocytes from nonsmokers as well as smokers, although the profile and extent of these adducts can vary among individuals. The relationship of the lymphocyte DNA adducts detected in this study to human cancer susceptibility remains to be determined. [ABSTRACT FROM PUBLISHER]