Effects of polychlorinated biphenyls on lung and liver tumors initiated in suckling mice by N-nitrosodimethylamine.

A mixture of polychlorinated biphenyls (PCB), Aroclor 1254, was administered ip (500 mg/kg) to pregnant Swiss noninbred CD-1 mice on the 19th day of gestation. The suckling offspring of these mice and of controls were then treated ip with 5 mg N-nitrosodimethylamine (DMN)/kg on postnatal day 4 or day 14. The progeny were killed at 28 weeks or 18 months of age. The DMN treatment caused lung and liver tumors. Among the mice given DMN on day 14, exposure also to PCB resulted in a lower tumor incidence in some of the treatment groups. This protective action was most evident for lung tumors in both sexes at 18 months of age and for liver tumors in males at 28 weeks. However, the PCB exposure also led to significant increases in the percentage of mice with extensive DMN-initiated liver tumors at 18 months of age compared to the results obtained when only DMN was given. This effect was most pronounced in mice given DMN on postnatal day 4.