Carcinogenesis, Vol 18, 523-529, Copyright © 1997 by Oxford University Press
W Baer-Dubowska, SV Vulimiri, RG Harvey, C Cortez and J DiGiovanni
The present study has analysed the DNA adducts formed in SENCAR mouse
epidermis following topical application of 7-methylbenz[a]anthracene (7-
MBA). Mice were treated with 400 nmol of 7-MBA, which represents an
initiating dose of this hydrocarbon for SENCAR mice. DNA adducts were
analysed 24 h after topical application of the hydrocarbon by 32P-
postlabeling coupled with either HPLC analysis or an improved TLC procedure
giving better resolution of DNA adducts through the use of a D6 solvent
[isopropanol:4N NH4OH (1:1)] following D5. Twenty-four hours after topical
application of 400 nmol 7-MBA, the level of total covalent binding was 0.37
+/- 0.07 pmol/mg DNA as determined by 32P- postlabeling. This level of
binding correlated well with the relative tumor initiating activity of this
hydrocarbon compared to 7,12- dimethylbenz[a]anthracene (6.4 +/- 0.01
pmol/mg DNA) and dibenz[a,j]anthracene (0.03 +/- 0.01 pmol/mg DNA).
Analysis of the 32P- labeled 3',5'-diphosphodeoxyribonucleosides by HPLC
and TLC revealed the presence of deoxyguanosine (dGuo) and deoxyadenosine
(dAdo) adducts formed from both the anti- and syn-bay-region diol-epoxides
of 7-MBA (anti- and syn-7-MBADEs). The major DNA adduct derived from 7-MBA
in mouse epidermis was tentatively identified as (+) anti-7-MBADE-trans-N2-
dGuo. In addition, a minor dGuo adduct derived from the bay-region syn-
diol-epoxide of 7-MBA was detected as well as a minor dAdo adduct from this
diol-epoxide. Another minor dAdo adduct was also detectably present which
arose from either the anti- or syn-diol epoxide. Furthermore, several
unidentified DNA adducts were present in both HPLC and TLC chromatograms of
DNA samples from 7-MBA-treated mice. These results are discussed in terms
of the role of specific 7-MBA-DNA adducts in tumor initiation by this
hydrocarbon.
ARTICLES
Analysis of 7-methylbenz[a]anthracene-DNA adducts formed in SENCAR mouse epidermis by 32P-postlabeling
The University of Texas M.D. Anderson Cancer Center, Science Park- Research Division, Smithville 78957, USA.
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