INTERACTION OF 3,4,5,3',4'-PENTACHLOROBIPHENYL AND 2,4,5,2',4',5'-HEXACHLOROBIPHENYL IN PROMOTION OF ALTERED HEPATIC FOCI IN RATS

This study was undertaken to investigate tumour promoting interactions of 2,4,5,2',4',5' -hexachlorobiphenyl (PCB 153) and 3,4,5,3',4'-penta chlorobiphenyl (PCB 126) in female Sprague-Dawley rats. Five weeks bef ore the promotion treatment, the rats were partially hepatectomized an d initiated with nitrosodiethylamine. The test substances were adminis tered by weekly, subcutaneous injections for 20 weeks. The results fro m this study suggest that treatment with a combination of these two co ngeners causes a more than additive effect on the formation of gamma-g lutamyltranspeptidase-positive hepatic foci. Co-exposure to PCB 126 an d PCB 153 caused a dose-dependent reduction of the PCB 153-induced CYP 2B1/B2-activity in these livers.