Identification of N-(deoxyguanosin-8-yl)-2-amino-3,4-dimethylimidazo[4,5-f]quinoline (dG-C8-MeIQ) as a major adduct formed by MeIQ with nucleotides in vitro with DNA in vivo.

The N-hydroxylamine of a carcinogenic heterocyclic amine, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), was reacted with four 2'-deoxynucleoside 3'-monophosphates after O-acetylation. 32P-Postlabeling analysis demonstrated that the adduct was formed with only the guanine nucleotide, and the structure of the compound in the obtained adduct spot was determined to be N-(deoxyguanosin-8-yl)-MeIQ 3',5'-diphosphate (3',5'-pdGp-C8-MeIQ). DNA samples from livers of mice fed MeIQ were also 32P labeled under standard conditions and additionally treated with nuclease P1 and phosphodiesterase I. A single adduct spot was obtained and the structure of the adduct was identified as 5'-pdG-C8-MeIQ. Thus, MeIQ binds at the C-8 position of guanine in vitro and in vivo, like other heterocyclic amines.