Polychlorinated biphenyl(s) as a promotor in experimental hepatocarcinogenesis in rats.

The effects of dietary polychlorinated biphenyls (PCBs) on hepatocarcinogenesis in female rats of Donryu strain receiving 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) were investigated. Oral administration of PCBs after administration of 3'-Me-DAB resulted in a high incidence (64%) of hepatocarcinoma. In contrast, administration of a similar amount of PCBs before, or together with 3'-Me-DAB did not induce hepatic tumors. Administration of a slightly larger amount of PCBs alone did not induce liver tumors, while administration of a slightly larger amount of 3'-Me-DAB alone caused only a low incidence (13%) of hepatocarcinoma. These results strongly suggest that PCBs exert a potent promoting action in experimental azo dye hepatocarcinogenesis.