The biotransformation of benzo[a]pyrene (BP) was studied in vitro in the presence of microsomal fractions of placental and fetal tissues from humans and monkeys (Macaca nemestrina). Metabolites formed in the incubation flasks were extracted and separated by means of high-pressure liquid chromatography utilizing a microparticulate column. In general, the formation of diols and quinones in fetal and placental homogenates was undetectable following 15-min incubations. The formation of phenolic metabolites, however, was easily measurable in fetal liver and lung and in the placenta but not in fetal spleen, kidney, pancreas or adrenal gland. The latter observation contrasted with high specific activities measured in the fetal adrenal gland with the fluorometric assay for aryl hydrocarbon hydroxylase activity. In placentas from cigarette smokers, relatively large quantities of an unidentified metabolite(s) appeared in metabolic profiles. This metabolite(s) did not co-chromatograph with any of the standard metabolites and the retention time was between those of the 9,10- and 4,5-diols. The same placental tissues catalyzed the covalent binding of BP to DNA and were far more active in this regard than any of the other fetal tissues investigated. The data indicated a correlation between metabolic profiles and capacity for catalyzing covalent binding to DNA for fetal/placental tissues.
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