Rapid release of carcinogen-guanine adducts from DNA after reaction with N-acetoxy-2-acetylaminofluorene or N-benzoyloxy-N-methyl-4-aminoazobenzene

Abstract

Reaction of N-benzoyloxy-N-methyl-4-aminoazobenzene (N-benzoyloxy-MAB) or N-acetoxy-N-acetyl-2-aminofluorene (N-acetoxy-AAF), model ultimate aromatic amine or amide carcinogens, with [purine-14C]DNA [from calf thymus] at pH 7.4 or reaction of N-hydroxy-2-aminofluorene (N-hydroxy-AF) at pH 4.6 resulted in the rapid release of 14C-containing products not precipitable with the DNA. Four such products were obtained on reaction with N-acetoxy-AAF, 2 with N-hydroxy-AF and 6 with N-benzoyloxy-MAB. Depending on the DNA sample used, the total amounts of 14C in these products from the reactions with N-benzoyloxy-MAB or N-acetoxy-AAF ranged from .apprx. 5% to as much as 30-40% of the amounts in the N-(deoxyguanosin-8-yl)-MAB or N-(deoxyguanosin-8-yl)-AAF residues in the DNA from the same reaction mixtures. Reactions with N-acetoxy-[acetyl-3H]AAF showed that the 2 major products retained the amide residue from the N-acetoxy-AAF. When the reactions were carried out with [guanine-(8-3H; 8-14C); adenine-(2,8-3H; 8-14C)]DNA, the 2 major products formed from N-acetoxy-AAF and 4 products formed from N-benzoyloxy-MAB had very low 3H:14C ratios; these ratios were those expected for guanine derivatives which had lost the 8-3H. Studies on the major DNA adducts N-(deoxyguanosin-8-yl)-MAB and N-(deoxyguanosin-8-yl)-AAF indicated that the new adducts were not formed from these nucleosides. Evidently the 2 major AAF products and the 4 MAB adducts studied are guanine derivatives formed by depurination of N-7 substituted adducts in the DNA.