title: The identification of bases in DNA involved in covalent binding of the reactive metabolite from 9-hydroxybenzo[a]pyrene.
abstract: Unlabelled 9-hydroxybenzo[a]pyrene (9-OH-BP) was incubated with a microsomal metabolic system and plasmid Col E1 DNA that had been radiolabelled by nick-translation with a tritiated deoxyribonucleotide. After the addition of an excess of a similar incubate that substituted calf thymus for plasmid DNA, a fraction obtained from DNA hydrolysates of these incubation mixtures was analysed by reverse-phase, h.p.l.c. for fluorescence and radioactivity of eluates. The presence of radioactivity with fluorescence activity in the same eluate fractions indicated the presence of 9-OH-BP-derived adducts with that radiolabelled nucleoside. These analyses showed the presence of at least four adducts with dG, a single adduct with dA, and no adducts with either dC or dT in plasmid DNA. This enabled the identification of components of similar h.p.l.c. profiles obtained from incubates with calf thymus DNA and [3H]9-OH-BP. No major qualitative or quantitative differences were found. As both the identities and extent of binding to these bases were similar to these previously reported for the ultimately carcinogenic BP- diolepoxides , we conclude that the non-carcinogenicity of 9-OH-BP is not, therefore, attributed to a difference in the base moieties involved in adduct formation. H.p.l.c. and spectrofluorimetric analyses indicated that an isolated metabolite of 9-OH-BP is indistinguishable from its 4,5-dihydrodiol. This is interpreted as evidence for the formation of 9-OH-BP-4,5-oxide as the reactive, DNA-binding intermediate.
mesh_terms: D000818:Animals; D003086:Bacteriocin Plasmids; D001580:Benzopyrenes / Q000378:metabolism / Q000633:toxicity*; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003087:Colicins / Q000235:genetics; D004247:DNA / Q000378:metabolism*; D003853:Deoxyribonucleosides / Q000032:analysis*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D010957:Plasmids; D014176:Protein Biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D013950:Thymus Gland
chemical_list: D001580:Benzopyrenes; D003087:Colicins; D003853:Deoxyribonucleosides; D004247:DNA; C023395:6-hydroxybenzo(a)pyrene