Metabolites of benzo(a) pyrene produced by placental microsomes from cigarette smokers and nonsmokers

Placental microsomes from a large majority of nonsmokers in this study showed almost undetectable specific activity in metabolizing benzo(a)pyrene (BaP) in vitro. The microsomal fraction of the placentas from individuals who smoked cigarettes during pregnancy had the highest activity in metabolizing BaP than other subcellular fractions. Cigarette smoking during pregnancy induced placental enzymes which converted BaP to a variety of metabolites: the yield of 3-hydroxy-BaP (3-OHBaP) and other phenols of BaP was the largest among the BaP metabolites, 7,8-dihydrodihydroxy-BaP (7,8-diol) having 13–72% the yield of 3-OHBaP. Other metabolites included 9, 10-dihydrodihydroxy-BaP (9,10-diol), 4,5-dihydrodihydroxy-BaP (4,5-diol), quinones of BaP and unidentified metabolites which were more polar than the diols.