title: The direct spectrophotometric observation of benzo(a)pyrene phenol formation by liver microsomes.
abstract: Optical spectral repetitive scan analysis during the oxidative metabolism of benzo(a)pyrene by liver microsomal suspensions reveals the time-dependent formation of an intermediate(s) of which the visible spectra resemble those of several benzo(a)pyrene phenols. Liver microsomes from 3-methylcholanthrene-treated rats showed a greater rate of formation of the phenols than did microsomes from control animals; the rate of formation catalyzed by liver microsomes from phenobarbital-pretreated rats was intermediate. When 3-hydroxybenzo(a)pyrene was used as a standard for comparison of activity, the rates of formation of phenols were compared when measured by fluorometric, spectrophotometric, or high-pressure liquid chromatographic analytical techniques. An epoxide hydrase inhibitor, 1,1,1-trichloropropene-2,3-oxide, enhanced phenol formation regardless of the source of liver microsomes, and 7,8-benzoflavone inhibited control and 3-methylcholanthrene-induced microsomal metabolism of benzo(a)pyrene, 7,8-Benzoflavone did not effect benzo(a)pyrene metabolism by liver microsomes from phenobarbital-pretreated rats. The effect of inhibitors on the spectrophotometric assay correlates well with the results obtained from benzo(a)pyrene metabolite analysis using high-pressure liquid chromatography.
mesh_terms: D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001580:Benzopyrenes / Q000378:metabolism*; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004988:Ethers, Cyclic / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006843:Hydrocarbons, Chlorinated / Q000494:pharmacology; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D010636:Phenols / Q000378:metabolism*; D051381:Rats; D013053:Spectrophotometry
chemical_list: D001580:Benzopyrenes; D004988:Ethers, Cyclic; D005419:Flavonoids; D006843:Hydrocarbons, Chlorinated; D010636:Phenols; D000249:Adenosine Monophosphate; D008748:Methylcholanthrene; D003577:Cytochrome P-450 Enzyme System; D010634:Phenobarbital