Xenobiotic-metabolising enzyme activities, PCBs and hydroxy-PCB metabolites in ringed seals from Svalbard and the Baltic Sea

Polychlorinated biphenyls (PCBs) are metabolised mainly by hepatic enzymes leading to formation of metabolites. This study investigates the induction of hepatic phase I and II enzymes and the formation of hydroxy (OH)-PCB metabolites in two contrasting ringed seal populations: highly contaminated Baltic Sea (n=31) and less contaminated Svalbard (n=21). Phase I (cytochrome P450) enzymes were measured as ethoxyresorufin O-deethylation (EROD), benzyloxyresorufin O-dealkylation (BROD), methoxyresorufin O-demethylation (MROD) and pentoxyresorufin O-dealkylation (PROD) activities, and phase II as uridine diphosphophate glucuronosyl transferase (UDPGT) and glutathione-s-transferase (GST). The induction of the enzymes was significantly higher in the Baltic ringed seals compared to Svalbard. The highly induced enzyme activity in the Baltic seals relative to seals from Svalbard is reflected in changes in PCB pattern and higher levels and differences in OH-PCB metabolite levels and patterns.