Cytochrome P450 1A response in North Sea Dab, Limanda limanda, from offshore and coastal sites

Dab (Limanda limanda) were collected at four stations in the southern North Sea in November 1993. Highest muscle polychlorinated biphenyl (PCB) concentrations were found at a station near the Dutch coast. CB153 was the dominant congener at all stations. Since the concentrations of two mono-ortho Cl-substituted congeners covaried strongly with CB153, this congener appears to be a good marker for general differences in PCB concentrations. Mean CB153 concentrations ranged from 50–160 ng g−1 lipid. The highest cytochrome P450 1A (CYP1A) levels were also found at the coastal station. The extent of induction, measured catalytically (7-ethoxyresorufin O-deethylase, EROD) and immunochemically (CYP1A ELISA), between the less contaminated offshore sites and the coastal site ranged up to five-fold. Both parameters were well correlated with muscle tissue PCB concentrations. The data indicate that the CYP1A induction response in dab populations along the Dutch coast is strong enough to separate the Dutch coastal area from more pristine offshore areas of the North Sea. Compared to results of previous studies in other seasons the present sampling period offered the best conditions to investigate the correlation between environmental contamination with PCBs and related compounds, since the variations in natural factors that also interfere, such as water temperature and condition of the fish, were very low.