title: Identification and quantitation of benzo[a]pyrene-DNA adducts formed by rat liver microsomes in vitro.
abstract: The two DNA adducts of benzo[a]pyrene (BP) previously identified in vitro and in vivo are the stable adduct formed by reaction of the bay-region diol epoxide of BP (BPDE) at C-10 with the 2-amino group of dG (BPDE-10-N2dG) and the adduct formed by reaction of BP radical cation at C-6 with the N-7 of Gua (BP-6-N7Gua), which is lost from DNA by depurination. In this paper we report identification of several new BP-DNA adducts formed by one-electron oxidation and the diol epoxide pathway, namely, BP bound at C-6 to the C-8 of Gua (BP-6-C8Gua) and the N-7 of Ade (BP-6-N7Ade) and BPDE bound at C-10 to the N-7 of Ade (BPDE-10-N7Ade). The in vitro systems used to study DNA adduct formation were BP activated by horseradish peroxidase or 3-methylcholanthrene-induced rat liver microsomes, BP 7,8-dihydrodiol activated by microsomes, and BPDE reacted with DNA. Identification of the biologically-formed depurination adducts was achieved by comparison of their retention times on high-pressure liquid chromatography in two different solvent systems and by comparison of their fluorescence line narrowing spectra with those of authentic adducts. The quantitation of BP-DNA adducts formed by rat liver microsomes showed 81% as depurination adducts: BP-6-N7Ade (58%), BP-6-N7Gua (10%), BP-6-C8Gua (12%), and BPDE-10-N7Ade (0.5%). Stable adducts (19% of total) included BPDE-10-N2dG (15%) and unidentified adducts (4%). Microsomal activation of BP 7,8-dihydrodiol yielded 80% stable adducts, with 77% as BPDE-10-N2dG and 20% of the depurination adduct BPDE-10-N7Ade. The percentage of BPDE-10-N2dG (94%) was higher when BPDE was reacted with DNA, and only 1.8% of BPDE-10-N7Ade was obtained.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha 68198-6805.
authors.forename: P D
authors.initials: PD
authors.lastname: Devanesan
authors.forename: N V
authors.initials: NV
authors.lastname: RamaKrishna
authors.forename: R
authors.initials: R
authors.lastname: Todorovic
authors.forename: E G
authors.initials: EG
authors.lastname: Rogan
authors.forename: E L
authors.initials: EL
authors.lastname: Cavalieri
authors.forename: H
authors.initials: H
authors.lastname: Jeong
authors.forename: R
authors.initials: R
authors.lastname: Jankowiak
authors.forename: G J
authors.initials: GJ
authors.lastname: Small
mesh_terms: D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide / Q000737:chemistry* / Q000378:metabolism; D000818:Animals; D001564:Benzo(a)pyrene / Q000737:chemistry*; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System; D004247:DNA / Q000737:chemistry*; D018736:DNA Adducts; D004101:Dihydroxydihydrobenzopyrenes / Q000737:chemistry* / Q000378:metabolism; D066298:In Vitro Techniques; D008862:Microsomes, Liver / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats
chemical_list: D018736:DNA Adducts; D004101:Dihydroxydihydrobenzopyrenes; C056612:benzo(a)pyrene-DNA adduct; C017228:benzo(a)pyrene 7,8-dihydrodiol; D001564:Benzo(a)pyrene; D015123:7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide; D004247:DNA; D003577:Cytochrome P-450 Enzyme System