title: Metabolism of benzo(a)pyrene by duck liver microsomes.
abstract: The metabolism of benzo(a)pyrene [BP], a model carcinogenic PAH, by hepatic microsomes of two duck species, mallard (Anas platyrhynchos) and common merganser (Mergus merganser americanus) collected from chemically-contaminated and relatively non-contaminated areas was investigated. The rate of metabolism of BP by liver microsomes of common merganser and mallard collected from polluted areas (2,650 +/- 310 and 2,200 +/- 310 pmol/min per mg microsomal protein, respectively) was significantly higher than that obtained with liver 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 P-450 1A1 was significantly higher in the liver microsomes of both duck species from the polluted areas as compared to the ducks from the non-polluted areas. The major BP metabolites, including BP-9, 10-diol, BP-4, 5-diol, BP-7, 8-diol, BP-1, 6-dione, BP-3, 6-dione, BP-6, 12-dione, 9-hydroxy-BP and 3-hydroxy-BP, formed by liver microsomes of both duck species from polluted and non-polluted areas, were qualitatively similar. However, the patterns of these metabolites were considerably different from each other. Liver microsomes of ducks from the polluted areas produced a higher proportion of benzo-ring dihydrodiols than the liver microsomes of ducks from the non-polluted areas, which converted a greater proportion of BP to BP-phenols. The predominant enantiomer of BP-7,8-diol formed by hepatic microsomes of the two duck species had an (-)R,R absolute stereochemistry. The data suggest that duck and rat liver microsomal enzymes have different regioselectivity but similar stereoselectivity in the metabolism of BP.
authors.affiliation: Environmental Toxicology and Chemistry Laboratory, Great Lakes Center for Environmental Research and Education, State University of New York College at Buffalo, 14222, USA.
authors.forename: S
authors.initials: S
authors.lastname: Honey
authors.forename: P
authors.initials: P
authors.lastname: O'Keefe
authors.forename: A T
authors.initials: AT
authors.lastname: Drahushuk
authors.forename: J R
authors.initials: JR
authors.lastname: Olson
authors.forename: S
authors.initials: S
authors.lastname: Kumar
authors.forename: H C
authors.initials: HC
authors.lastname: Sikka
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000737:chemistry / Q000378:metabolism*; D002273:Carcinogens / Q000633:toxicity; D019363:Cytochrome P-450 CYP1A1 / Q000096:biosynthesis; D004101:Dihydroxydihydrobenzopyrenes / Q000633:toxicity; D004372:Ducks; D004790:Enzyme Induction / Q000187:drug effects; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D008968:Molecular Conformation
chemical_list: D002273:Carcinogens; D004101:Dihydroxydihydrobenzopyrenes; C017228:benzo(a)pyrene 7,8-dihydrodiol; D001564:Benzo(a)pyrene; D019363:Cytochrome P-450 CYP1A1