Modulation of microsome-mediated benzo[a]pyrene-metabolism by serum

The effects of serum on the metabolism of benzo[a]pyrene (BP) by liver microsomes from 3-methylcholanthrene-treated rats were studied. In the presence of serum, the aryl hydrocarbon hydroxylase activities were enhanced to 160-570% of the control value. Enhancement of BP-metabolism by serum was also revealed by high performance liquid chromatography, but the relative amounts of a series of BP-metabolites were not changed appreciably by addition of serum. Binding of BP-metabolites to DNA was influenced by serum: adducts derived from two stereo-isomeric BP-7,8-di-hydrodiol-9,10-oxides were increased, while those from 9-hydroxybenzo[a]pyrene-4,5-oxide were reduced.