Interactive effects of CB 126 and benzo[a]pyrene on biotransformation enzymes, metabolites in bile and DNA adducts in the dab (Limanda limanda)

Two experiments were performed to study the interaction between 3,3′,4,4′,5-pentachlorobiphenyl (CB 126) and benzo[a]pyrene (BaP) in dab (Limanda limanda). The first experiment involved four groups: a group pretreated with 10 μg/kg CB 126 which was exposed to 2 mg/kg BaP 6 days later, groups treated with CB 126 and BaP only and a control group. The second experiment was similar, except the BaP dosage level was 50 mg/kg. CB 126 caused a shift in the pattern of BaP metabolites in bile of dab treated with 2 mg/kg BaP, but no such shift could be observed in the dab treated with 50 mg/kg BaP. This correlated with ethoxyresorufin-O-deethylase (EROD) induction which occurred only after exposure to CB 126 or 50 mg/kg BaP. Further, pretreatment with CB 126 caused a decreased amount of BaP DNA adducts formed after treatment with 50 mg/kg BaP. Glutathione S-transferase (GST) activities were not affected by any of the treatments. The results suggest that the pattern of metabolites in bile depends on cytochrome P450 induction status, whereas the amount of DNA adducts formed does not.