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  • Title: Syntheses of DNA adducts of two heterocyclic amines, 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) and 2-amino-9H-pyrido[2,3-b]indole (AalphaC) and identification of DNA adducts in organs from rats dosed with MeAalphaC.
    Author: Frederiksen H, Frandsen H, Pfau W.
    Journal: Carcinogenesis; 2004 Aug; 25(8):1525-33. PubMed ID: 15059926.
    Abstract:
    2-Amino-3-methyl-9H-pyrido[2,3-b]indole (MeAalphaC) and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (AalphaC) are mutagenic and carcinogenic heterocyclic amines formed during ordinary cooking. MeAalphaC and AalphaC are activated to mutagenic metabolites by cytochrome P450-mediated N-oxidation to the corresponding N2-OH derivatives. The proximate mutagenic N2-OH derivatives of MeAalphaC and AalphaC did not react with deoxynucleosides or DNA. However, upon acetylation with acetic anhydride both reacted with 2'-deoxyguannosine and 3'-phospho-2'-deoxyguanosine, resulting in one adduct each, but not with other nucleosides or nucleotides. The adducts were identified as N2-(2'-deoxyguanosin-8-yl)-MeAalphaC, N2-(2'-deoxyguanosin-8-yl)-AalphaC, N2-(3'-phospho-2'-deoxyguanosin-8-yl)-MeAalphaC and N2-(3'-phospho-2'-deoxyguanosin-8-yl)-AalphaC by comparison with adducts of known structure obtained by reaction of the parent amines with acetylated guanine N3-oxide. N2-OH-MeAalphaC and N2-OH-AalphaC reacted with calf thymus DNA after addition of acetic anhydride. 32P-postlabelling analysis of modified DNA showed one major adduct co-migrating with N2-(3',5'-diphospho-2'-deoxyguanosin-8-yl)-MeAalphaC and N2-(3',5'-diphospho-2'-deoxyguanosin-8-yl)-AalphaC, respectively. Some minor adducts presumed to be undigested oligomers were also detected. 32P-postlabelling analysis of DNA from several organs of rats dosed orally with MeAalphaC showed that in vivo N2-(2'-deoxyguanosin-8-yl)-MeAalphaC also was the major adduct formed. Relative adduct level in DNA isolated from the liver of the rats was about 50.40 adducts/10(9) nt. The adduct levels were approximately 4-fold lower in the colon and the heart and approximately 12-fold lower in the kidney of the rats.
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