title: Formation of benzylic-DNA adducts resulting from 7,12-dimethylbenz[a]anthracene in vivo.
abstract: Studies were undertaken to determine the formation of benzylic-DNA adducts in rats administered 7,12-dimethylbenz[a]anthracene (DMBA) and its meso-region metabolites by subcutaneous injection. Here, we show that 7-hydroxymethyl-12-methylbenz[a]anthracene (7-HMBA) and 7-sulfoxymethyl-12-methylbenz[a]anthracene (7-SMBA) gave rise to some benzylic-DNA adducts indistinguishable from adducts formed from DMBA. Adducts were analyzed by butanol enrichment-mediated 32P-postlabeling assay. Female Sprague-Dawley rats given a combined dose of 420 micromol DMBA/kg b. wt resulted in two major and up to nine minor adducts in the subcutaneous tissue, with chromatographic resemblance to benzylic-DNA adducts prepared in vitro. Subcutaneous administration of 7-HMBA, 7-SMBA, and 7-methyl-12-hydroxymethylbenz[a]anthracene (12-HMBA) (210, 42, and 210 micromol/kg b. wt, respectively) each resulted in one major and several minor benzylic-DNA adducts. From cochromatography with reference adducts, it was concluded that the benzylic DNA adduct 4, derived from the parent compound, comigrates with the major adduct from 7-HMBA and 7-SMBA, whereas adducts 2 and 3 comigrate with adducts resulting from 12-HMBA and 7-methyl-12-sulfooxymethylbenz[a]anthracene, respectively. These data suggest that 7-sulfooxymethyl- and 12-sulfooxymethy derivatives produce distinct adducts. Several major and minor diol epoxide-related DNA adducts were also detected. The diol epoxide- and benzylic-DNA adducts were found in a 2:1 ratio. The oral, intraperitoneal, and intramammiliary treatments with DMBA showed no detectable benzylic adducts in the liver and mammary glands 24 h after the last treatment, although the adduct formation was clearly evident with SMBA and/or HMBA treatments, suggesting that hydroxylation of DMBA to form HMBA may be the rate-limiting step for the meso-methyl substitution pathway. The present study clearly demonstrates the in vivo formation of benzylic-DNA adducts from DMBA. The data also reveal the involvement of the 12-methyl group of DMBA in adduct formation.
authors.affiliation: Department of Pharmacology and Toxicology, Brown Cancer Center, University of Louisville, Louisville, Kentucky 40202, USA.
authors.forename: M N V
authors.initials: MN
authors.lastname: Ravi Kumar
authors.forename: Manicka V
authors.initials: MV
authors.lastname: Vadhanam
authors.forename: Jamie
authors.initials: J
authors.lastname: Horn
authors.forename: James W
authors.initials: JW
authors.lastname: Flesher
authors.forename: Ramesh C
authors.initials: RC
authors.lastname: Gupta
mesh_terms: D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism*; D000818:Animals; D002855:Chromatography, Thin Layer; D018736:DNA Adducts / Q000378:metabolism*; D005260:Female; D051381:Rats; D017207:Rats, Sprague-Dawley; D012867:Skin / Q000378:metabolism
chemical_list: D018736:DNA Adducts; D015127:9,10-Dimethyl-1,2-benzanthracene