Microsome-mediated bioactivation of dibenzo[a,l]pyrene and identification of DNA adducts by 32P-postlabeling.
Dibenzo[a,l]pyrene (DBP) is one of the most potent bacterial mutagen and mammary carcinogens. When DBP (50 microM) was incubated with calf thymus DNA (300 microg/ml) in the presence of liver microsomes from beta-naphthoflavone (beta-NF)- or Aroclor 1254-treated rats, at least eight adduct spots were detected as analyzed by nuclease P1-enhanced 32P-postlabeling assay. DNA adduction was enhanced by nearly 20- and 60-fold with beta-NF- and Aroclor 1254-induced microsomes, respectively, as compared with uninduced microsomes, suggesting a possible involvement of CYP1A family in DBP activation. Inclusion of the selective P4501A1 inhibitor, alpha-naphthoflavone (50 microM) in the activation reaction almost completely (>98%) abolished adduct formation further supporting involvement of P4501A in DBP activation. Analysis of DNA and 2'-deoxynucleosides 3'-mononucleotide reacted with anti- and syn-DBP-11,12-diol-13,14-epoxides (DBPDEs) and co-chromatography analyses in multiple solvents showed that the microsomal DBP-DNA adducts were derived by interaction of both anti- and syn-DBPDEs with adenine and guanine in DNA in the following order: anti-DBPDE-dA approximately syn-DBPDE-dG >> anti-DBPDE-dG approximately syn-DBPDE-dA. It is concluded that (i) most or all DBP adducts were P4501A-mediated; (ii) both the anti- and syn-stereoisomers were involved in the DNA adduct formation; and (iii) both adenine and guanine in the DNA contributed equally to the formation of the major and minor adducts.
Arif
J M
JM
Preventive Medicine and Environmental Health, University of Kentucky Medical Center, Lexington 40536, USA.
Gupta
R C
RC
D000818:Animals; D001140:Aroclors / Q000633:toxicity; D001580:Benzopyrenes / Q000378:metabolism*; D002273:Carcinogens / Q000633:toxicity; D020111:Chlorodiphenyl (54% Chlorine); D002845:Chromatography; D019363:Cytochrome P-450 CYP1A1 / Q000378:metabolism; D018736:DNA Adducts / Q000032:analysis / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D019324:beta-Naphthoflavone / Q000494:pharmacology
D001140:Aroclors; D001580:Benzopyrenes; D002273:Carcinogens; D018736:DNA Adducts; D004791:Enzyme Inhibitors; D009711:Nucleotides; D020111:Chlorodiphenyl (54% Chlorine); D019324:beta-Naphthoflavone; D019363:Cytochrome P-450 CYP1A1; C041517:dibenzo(a,l)pyrene