The uptake and distribution of [ 3H]benzo[ a]pyrene in the Northern pike ( Esox lucius). Examination by whole-body autoradiography and scintillation counting

The uptake and distribution of the polyaromatic hydrocarbon benzo[ a]pyrene in Northern pike ( Esox lucius) were investigated by whole body autoradiography and scintillation counting. [ 3H]Benzo[ a]pyrene was administered either in the diet or in the water. The levels of this xenobiotic employed corresponded to levels found in moderately polluted water. The uptake and distribution of this compound and its metabolites were followed from 10 hr to 21 days after the initial exposure. The autoradiography patterns observed here with both routes of administration suggest, as expected, that benzo[ a]pyrene is taken up through the gastrointestinal system and the gills, metabolized in the liver, and excreted in the urine and bile. Other findings indicate that the gills may not be a major route of excretion for benzo[ a]pyrene and its metabolites in the Northern pike; that benzo[ a]pyrene may be taken up from the water directly into the skin of this fish; that benzo[ a]pyrene and its metabolites are heterogeneously distributed in the kidney of the Northern pike; and that very little radioactivity accumulates in the adipose tissue. With scintillation counting, uptake of radioactivity from the water was found to occur rapidly in all organs, reaching a plateau in most cases after about 0.8 days. The concentrations of radioactivity in different organs ranged between 50 (many organs) and 80,000 (gallbladder + bile) times that found in the surrounding water. Since most of the radioactivity recovered in different organs of the pike after 8.5 days of exposure was in the form of metabolites, we feel that metabolism may play an important role in the bioconcentration of xenobiotics in fish.