Carcinogenesis, Vol 18, 1999-2007, Copyright © 1997 by Oxford University Press
JM Arif and RC Gupta
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.
ARTICLES
Microsome-mediated bioactivation of dibenzo[a,l]pyrene and identification of DNA adducts by 32P-postlabeling
Preventive Medicine and Environmental Health, University of Kentucky Medical Center, Lexington 40536, USA.
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