Products formed from the in vitro reaction of metabolites of 3-aminochrysene with calf thymus DNA

Abstract

3-Aminochrysene, a mutagenic geometric isomer of the mutagenic and carcinogenic aromatic amine 6-aminochrysene, has been synthesized and its metabolic activation studied by characterization of the products formed from the reaction of metabolites with calf thymus DNA. DNA adducts produced by 3-aminochrysene via N-oxidation were examined by preparing 3-nitrosochrysene and incubating the nitroso derivative with calf thymus DNA in the presence of ascorbic acid (to generate the N-hydroxy derivative) at pH 5. The major adduct, as determined by 1H-NMR and thermospray-mass spectrometry of the modified nucleoside obtained after enzymatic hydrolysis of the modified DNA, was N-(deoxyguanosin-8-yl)-3-aminochrysene. Thus, the reaction of N-hydroxy-3-aminochrysene with DNA differs from that of N-hydroxy-6-aminochrysene, which had previously been shown to generate N-(deoxyguanosin-8-yl)-6-aminochrysene, 5-(deoxyguanosin- N 2-yl)-6-aminochrysene and N-(deoxyinosin-8-yl)-6-aminochrysene as major adducts. 32P-Postlabeling analysis of DNA treated with 3-aminochrysene in the presence of liver microsomes from rats pretreated with phenobarbital indicated an adduct pattern identical to that seen with DNA that had been treated with 3-nitrosochrysene and ascorbic acid. However, DNA treated with 3-aminochrysene (3-AC) in the presence of liver microsomes from rats pretreated with 3-methylcholanthrene contained a major adduct that was chromatographically distinct from N-(deoxyguanosin-8-yl)-3-aminochrysene.