Formation of DNA adducts in 10T1/2 mouse embryo fibroblasts incubated with benzo(a)pyrene or dihydrodiol oxide derivatives.

Abstract

Abstract Binding of benzo( a )pyrene (BP) metabolites to DNA was studied in the mouse embryo fibroblast 10T½ cell line. The cells metabolized BP to its diastereoisomeric 7,8-dihydrodiol-9,10-oxides, (±)-7β, 8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene and (±)-7β,8α-dihydroxy-9β,10β-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene, which formed covalent adducts with cellular DNA. Detailed analysis by high-pressure liquid chromatography indicated that a deoxyguanosine adduct, N 2 -(10 S -[7 R ,8 S ,9 R -trihydroxy-7,8,9,10-tetrahydrobenzo( a )pyrene]yldeoxyguaninosine, was the predominant DNA adduct formed in cells exposed to BP. This adduct is also the major one found in human tissues exposed to BP. Exposure of cells to (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene and (±)-7β,8α-dihydroxy-9β,10β-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene, rather than to BP, produced several additional adducts on DNA. During a 68-hr posttreatment incubation, about 50 to 70% of the adducts were removed from the cellular DNA. No major differences between the relative rates of excision from cellular DNA of the individual (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene and (±)-7β,8α-dihydroxy-9β,10β-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene adducts were found. These results provide evidence that when 10T½ cells are exposed to BP there is stereoselective synthesis and covalent binding of BPDE mainly to the N 2 group of deoxyguanosine. This similarity with results obtained in human tissues makes the 10T½ cell an attractive model system for studying the action of BP and related polycyclic hydrocarbons.