DNA adducts in cultures of polychlorinated biphenyl-treated human hepatocytes

Polychlorinated biphenyls (PCBs) are persistent environmental chemicals that accumulate at the apex of food chains. Several scientific committees support its designation as a human carcinogen, even though the precise mechanism of carcinogenesis remains controversial. In view of its uncertain ability to cause DNA damage in human liver, we investigated the effects of Aroclor 1254, Aroclor 1016, and 4-chlorobiphenyl (4-CB) on DNA adduct formation in cultures of primary human hepatocytes from five donors. Based on (32)P-postlabeling assays, we detected DNA adducts in native human liver as well as untreated, i.e., control cultures of human hepatocytes. Treatment of human hepatocytes with Aroclor 1016 and Aroclor 1254 resulted in four-fold (NP1) and seven-fold (butanol) increases in DNA adduct formation. Further, two and six new adduct spots were detected by multidirectional thin-layer chromatography after nuclease P1 and butanol enrichment. Treatment of human hepatocyte cultures with 4-CB led to 209 adducts per 10(9) nucleotides at the 60 microM concentration, and we show metabolically activated PCBs to be more efficient in the production of DNA-binding species compared with higher chlorinated PCB mixtures. Our study is therefore highly suggestive for a link between PCB exposure and DNA insult in human hepatocytes.