Effects of benzo(a)pyrene, 3,3′,4,4′-tetrachlorobiphenyl and 2,2′,4,4′,5,5′-hexachlorobiphenyl on the xenobiotic-metabolizing enzymes in the mussel ( Mytilus galloprovincialis)

Abstract

Benzo(a)pyrene (BaP), 3,3′,4,4′-tetrachlorobiphenyl (TCB) and 2,2′,4,4′,5,5′-hexachlorobiphenyl were tested for their ability to induce hepatic xenobiotic metabolizing enzymes in a marine mussel. TCB and BaP (two planar molecules), but not HCB (a bulky PCB), increased phase I enzyme parameters including the P-450 content, NADPH cytochrome c reductase activity and BaP oxidase activity. The glutathione S-transferase activity and glutathione content increased in HCB-treated mussels and decreased or remained the same as in the control in BaP- and TCB-exposed animals. Epoxide hydrolase (EH) activity increased in BaP- and HCB- but not in TCB-treated groups. These results show that, as in fish, only 3-methylcholanthrene P-450-type inducers (BaP and TCB, a non- ortho-substituted PCB) and not the phenobarbital P-450-type inducer (HCB, a di- ortho-substituted PCB) are effective inducers of phase I enzymes in mussel at the doses tested. Phase II activities were more sensitive to BaP and HCB than to TCB treatment.