COMPARATIVE METABOLISM OF BENZO(A)PYRENE, CHRYSENE AND PHENANTHRENE BY BROWN BULLHEAD LIVER-MICROSOMES

The metabolism of benzo(a)pyrene (BaP), chrysene and phenanthrene by l iver microsomes of brown bullhead (Ictalurus nebulosus) was investigat ed. Among the three PAHs, BaP was metabolized at the highest rate, chr ysene at an intermediate rate and phenanthrene at the lowest rate. The liver microsomes from the control fish metabolized all three PAHs to their corresponding K-region dihydrodiols to a small extent. A greater proportion of diols with a bay-region double bond (proximate carcinog enic metabolites) than of bay-region diols was formed from the three P AHs, but the proportion of diols with a bay-region double bond varied with the hydrocarbon. Metabolically-formed BaP-7,8-diol, chrysene-1,2- diol and phenithrene 1,2-diol consisted predominantly of the R,R enant iomer. The data show that brown bullhead liver microsomes metabolize t he three PAHs, which vary in molecular size and shape, with essentiall y similar regio- and stereoselectivity.