Interaction of 3,4,5,3′,4′‐Pentachlorobiphenyl and 2,4,5,2′,4′,5′‐Hexachlorobiphenyl in Promotion of Altered Hepatic Foci in Rats

Abstract

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'-pentachlorobiphenyl (PCB 126) in female Sprague-Dawley rats. Five weeks before the promotion treatment, the rats were partially hepatectomized and initiated with nitrosodiethylamine. The test substances were administered by weekly, subcutaneous injections for 20 weeks. The results from this study suggest that treatment with a combination of these two congeners causes a more than additive effect on the formation of gamma-glutamyltranspeptidase-positive hepatic foci. Co-exposure to PCB 126 and PCB 153 caused a dose-dependent reduction of the PCB 153-induced CYP2B1/B2-activity in these livers.