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

Abstract

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.