title: [The role of secondary metabolism in formation of benz(a)pyrene dihydrodiol profile in microsome membranes].
abstract: 4,5-, 7,8- and 9,10-dihydrodiols of benz(a)pyrene (BP) were separated by thin-layer chromatography and their influence on BP-hydroxylase activity was studied in liver microsomes isolated from rats treated with phenobarbital (PB-microsomes) and 3-methylcholanthrene (MC-microsomes). All diols studied inhibited hydroxylation of BP by the competitive type. Accumulation of BP-diols in the incubation media correlated with their affinity to cytochrome P-450 isoenzymes which catalyzed the secondary metabolism of these diols. This correspondence allowed to formulate the kinetic and temperature dependence of BP oxidation suggesting that two main groups of hemoprotein isoforms were contained which were dissimilar in the active site orientation. Treatment with 3-methylcholanthrene induced specifically those hemoproteins which had the active site directed inside the membrane lipids; treatment with phenobarbital involved induction of two groups of hemoproteins active site of which was directed both to lipid and to water. The primary metabolism of the hydrophobic BP involved cytochrome P-450 isoenzymes which had the active site directed inside the lipids; the secondary metabolism of more polar diols was realized using both groups of hemoprotein isoenzymes with active sites oriented into lipids and water.
authors.forename: M V
authors.initials: MV
authors.lastname: Izotov
authors.forename: V M
authors.initials: VM
authors.lastname: Shcherbakov
authors.forename: Ia M
authors.initials: IaM
authors.lastname: Koen
authors.forename: V M
authors.initials: VM
authors.lastname: Devichenskiĭ
authors.forename: S M
authors.initials: SM
authors.lastname: Spiridonova
authors.forename: L V
authors.initials: LV
authors.lastname: Lugovaia
authors.forename: S A
authors.initials: SA
authors.lastname: Benediktova
mesh_terms: D000818:Animals; D001579:Benzopyrene Hydroxylase / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D004101:Dihydroxydihydrobenzopyrenes / Q000378:metabolism* / Q000633:toxicity; D004790:Enzyme Induction; D006900:Hydroxylation; D007425:Intracellular Membranes / Q000201:enzymology / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000201:enzymology / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D011919:Rats, Inbred Strains
chemical_list: D004101:Dihydroxydihydrobenzopyrenes; D008748:Methylcholanthrene; D001579:Benzopyrene Hydroxylase; D010634:Phenobarbital
vernacular_title: Rol' vtorichnogo metabolizma v formirovanii profilia digidrodiolov benz(a)pirena v membranakh mikrosom.