Identification of N-(Deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo [4,5-b]pyridine as the major adduct formed by the food-borne carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, with DNA.
The covalent binding of the N-acetoxy-, N-hydroxy-, and nitro derivatives of the food-borne carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) to 2'-deoxyribonucleosides or DNA was investigated in vitro and in vivo. N-Acetoxy-PhIP reacted with deoxyguanosine (dG), but not with the other deoxyribonucleosides, to form N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP), whose structure was determined by NMR and mass spectral analyses and by ultraviolet absorption and pH-solvent partitioning characteristics. While reaction of N-acetoxy-PhIP with calf thymus DNA at pH 5.0 yielded 5.38 +/- 1.16 nmol of bound PhIP residues/mg of DNA, N-hydroxy-PhIP gave only 0.13-0.23 nmol binding/mg of DNA under identical reaction conditions. Nitro-PhIP produced no detectable binding under these conditions. HPLC analysis of 1-butanol extracts of enzymatically hydrolyzed DNA that had been modified by N-acetoxy-PhIP in vitro showed a major adduct which coeluted with and had an ultraviolet absorption and a mass spectrum that were identical to that of authentic dG-C8-PhIP. 32P-Postlabeling analysis of DNA isolated from colon, pancreas, lung, heart, and liver of rats treated orally with PhIP revealed the presence of a major PhIP-DNA adduct. This adduct had chromatographic properties identical to that of the 32P-labeled bis(phosphate) derivative of dG-C8-PhIP and represented 35-45% of the total adducts.(ABSTRACT TRUNCATED AT 250 WORDS)
Lin
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Office of Research (HFT-100), National Center for Toxicological Research, Jefferson, Arkansas 72079.
Kaderlik
K R
KR
Turesky
R J
RJ
Miller
D W
DW
Lay
J O
JO
Kadlubar
F F
FF
D000818:Animals; D003106:Colon / Q000737:chemistry; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism*; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism* / Q000633:toxicity; D066298:In Vitro Techniques; D008099:Liver / Q000737:chemistry; D008168:Lung / Q000737:chemistry; D009153:Mutagens / Q000737:chemistry / Q000378:metabolism*; D009206:Myocardium / Q000737:chemistry; D010179:Pancreas / Q000737:chemistry; D010759:Phosphorus Isotopes; D051381:Rats
D007093:Imidazoles; D009153:Mutagens; D010759:Phosphorus Isotopes; C078255:N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; D004247:DNA; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; D003849:Deoxyguanosine