Analysis of 7-methylbenz[a]anthracene-DNA adducts formed in SENCAR mouse epidermis by 32P-postlabeling.
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.
Baer-Dubowska
W
W
The University of Texas M.D. Anderson Cancer Center, Science Park-Research Division, Smithville 78957, USA.
Vulimiri
S V
SV
Harvey
R G
RG
Cortez
C
C
DiGiovanni
J
J
D000818:Animals; D001551:Benz(a)Anthracenes / Q000032:analysis / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D018736:DNA Adducts / Q000032:analysis*; D003839:Deoxyadenosines / Q000032:analysis*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000032:analysis; D004817:Epidermis / Q000737:chemistry / Q000187:drug effects*; D005260:Female; D051379:Mice; D018632:Mice, Inbred SENCAR; D010761:Phosphorus Radioisotopes / Q000032:analysis
C105077:7-MBADE-N(2)-deoxyguanosine; C105079:7-MBADE-N(6)-deoxyadenosine; D001551:Benz(a)Anthracenes; D002273:Carcinogens; D018736:DNA Adducts; D003839:Deoxyadenosines; D010761:Phosphorus Radioisotopes; C069753:7-methylbenz(a)anthracene 3,4-dihydrodiol 1,2-epoxide; C021219:7-methylbenzanthracene; D003849:Deoxyguanosine