Cytochrome P-450 forms and its inducibility by PCB isomers in black-headed gulls and black-tailed gulls

The specific profile of hepatic drug-metabolizing enzymes and isomer-specific residue of PCBs were characterized in the same family of sea gulls such as black-headed gull (Larus ridibundus) and black-tailed gull (Larus crassirostris). The examined enzyme contents and activities were higher in the former species. On the other hand, higher residual level of polychlorinated biphenyls (PCBs) were observed in black-tailed gull. There was no relationship between PCB concentrations and any enzyme activities in both species. A significant correlation between 2,3,7,8-TCDD toxicity equivalents (TEQs) of coplanar PCBs in pectoral muscles and 7-ethoxyresorufin O-deethylase activities in liver microsomes was observed only in black-headed gulls. According to the electrophoretic/immunochemical analysis using antibodies raised against rat P-450 enzymes, it was clear that both birds have the gull P-450 2B protein which is homologous with rat P-450 2B1. However, gull P-450 1A1 and gull P-450 1A2 (these are homologous protein with rat P-450 1A1 and rat P-450 1A2 respectively) were detected only in liver microsomes of black-headed gull. The variation in contents of these P-450 molecular species in these birds are discussed in relation to induction by PCBs.