Cytochrome P450-mediated enzyme activities and polychlorinated biphenyl accumulation in harp seal (Phoca groenlandica)

The presence and activities of hepatic cytochrome P450 (CYP) isoforms in Ba rents Sea harp seals (n = 13) were studied using catalytic activities, sele ctive inhibitors, and western blots. In addition the polychlorinated biphen yl (PCB) burden was measured in both the blubber and the food of the seals. The CYP activities and CYP isoforms present were related to the blubber PC B load and the relative presence of each PCB congener in seals relative to their food (metabolic index). The CYP activities measured were:2-7 times hi gher than in ringed and harp seals from other studies, suggesting induction due to contaminant exposure. However, PCB burdens were surprisingly low an d were not related tol the CYP activities. Probably these high activities w ere due to exposure to other contaminants or due to the diet consisting mai nly of crustaceans, which are rich in carotenes. Carotenes. have been shown to be potent CYP inducers in several laboratory animals. The CYP studies i ndicated the presence of CYP1A, -2B and -3A isoforms. A decrease in the rel ative presence of a number of PCB congeners in seal blubber relative to the ir food, supposed to be due to CYP-mediated metabolism, corresponded with t he metabolic capabilities of the CYP isoforms found. (C) 1999 Elsevier Scie nce Ltd. All rights reserved.