Metabolism of benzo(a)pyrene by duck liver microsomes

The metabolism of benzo(a)pyrene [BP], a model carcinogenic PAH, by hepatic microsomes of two duck species, mallard (Anas platyrhynchos) and common me rganser (Mergus merganser americanus) collected from chemically-contaminate d and relatively non-contaminated areas was investigated. The rate of metab olism of BP by liver microsomes of common merganser and mallard collected f rom polluted areas (2650 +/- 310 and 2200 +/- 310 pmol/min per mg microsoma l protein, respectively) was significantly higher than that obtained with l iver microsomes of the two species collected from non-polluted areas (334 /- 33 and 231 +/- 30 pmol/min per mg microsomal protein. respectively). The level of cytochrome P450 1A1 was significantly higher in the liver microso mes of both duck species from the polluted areas as compared to the ducks f rom the non-polluted areas. The major BP metabolites, including BP-9, 10-di ol, BP-4, 5-diol, BP-7, 8-diol, BP-1, 6-dione, BP-3, 6-dione, BP-6, 12-dion e, 9-hydroxy-BP and 3-hydroxy-BP, formed by liver microsomes of both duck s pecies from polluted and non-polluted areas, were qualitatively similar. Ho wever, the patterns of these metabolites were considerably different from e ach other. Liver microsomes of ducks from the polluted areas produced a hig her proportion of benzo-ring dihydrodiols than the liver microsomes of duck s from the non-polluted areas, which converted a greater proportion of BP t o BP-phenols. The predominant enantiomer of BP-7,8-diol formed by hepatic m icrosomes of the two duck species had an (-)R,R absolute stereochemistry. T he data suggest that duck and rat liver microsomal enzymes have different r egioselectivity but similar stereoselectivity in the metabolism of BP. (C) 2000 Elsevier Science Inc. All rights reserved.