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.
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.
Frederiksen
Hanne
H
Institute of Food Safety and Nutrition, Danish Veterinary and Food Administration, Mørkhøj Bygade 19, DK 2860 Søborg, Denmark. haf@fdir.dk
Frandsen
Henrik
H
Pfau
Wolfgang
W
D000089:Acetic Anhydrides / Q000737:chemistry; D000818:Animals; D002243:Carbolines / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D004247:DNA / Q000737:chemistry; D018736:DNA Adducts; D007477:Ions; D008099:Liver / Q000378:metabolism; D008297:Male; D008956:Models, Chemical; D009153:Mutagens; D051381:Rats; D017208:Rats, Wistar; D013696:Temperature; D013950:Thymus Gland / Q000378:metabolism; D013997:Time Factors; D014466:Ultraviolet Rays
D000089:Acetic Anhydrides; D002243:Carbolines; D018736:DNA Adducts; D007477:Ions; D009153:Mutagens; C017821:2-amino-3-methyl-9H-pyrido(2,3-b)indole; C031800:acetic anhydride; D004247:DNA; C017822:2-amino-9H-pyrido(2,3-b)indole