Metabolism of 2-acetylaminofluorene in the chinese hamster ovary cell mutation assay

Publisher Website
Google Scholar
Abstract
Chinese hamster ovary (CHO) cells were exposed to 2‐acetylaminofluorene (2‐AAF) and 2‐aminofluorene (2‐AF), and several of their N‐oxidized metabolites in order to study the mechanisms by which arylamides and arylamines produce mutations in mammalian cells. The number of mutations induced at the hypoxanthine‐guanine phosphoribosyl transferase locus by each compound (mutants/106 CHO cells/nmol compound/ml) was estimated to be: N‐acetoxy‐2‐AAF, 310; N‐hydroxy‐2‐AF, 3; N‐hydroxy‐2‐AAF (with and without hepatic S9 activation), 0.7; 2‐AAF (with S9), 0.1; and 2‐AF (with S9), 0.09. With each compound, DNA adducts were also identified and quantified, and in all cases the major adduct was N‐(deoxyguanosin‐8‐yl)‐2‐AF. 2‐AAF and N‐hydroxy‐2‐AAF also formed minor amounts of N(deoxyguanosin‐8‐yl)‐2‐AAF and 3‐(deoxyguanosin‐N2‐yl)‐2‐AAF. The relationship between mutation induction and adduct formation for each of the derivatives was similar to that previously reported for N‐hydroxy‐2‐AF. Inclusion of the deacetylase inhibitor, paraoxon, reduced the mutagenicity of 2‐AAF, N‐hydroxy‐2‐AAF and N‐acetoxy‐2‐AAF, and the DNA adducts produced by N‐acetoxy‐2‐AAF to background levels. Acetyl coenzyme A increased the mutations and CHO cytosol‐mediated DNA binding of N‐hydroxy‐2‐AAF, but did not substantially increase these responses from N‐hydroxy‐2‐AF. N‐Hydroxy‐2‐AAF was not detectably metabolized by CHO cells. Taken together, these data indicate that CHO cells metabolized N‐acetoxy‐2‐AAF to a reactive derivative by N‐deacetylation to N‐acetoxy‐2‐AF, while N‐hydroxy‐2‐AF reacted direcitly with DNA. The major pathway of N‐hydroxy‐2‐AAF activation appeared to be an initial O‐acetylation to N‐acetoxy‐2‐AAF and this occurred to only a limited extent in the CHO cells. N‐Hydroxy‐2‐AAF also seemed to form an additional unknown ester intermediate that gave rise to acetylated DNA adducts. The limited O‐acetylase activity in CHO cells appeared to cntribute to the low sensitivity of these cells toward mutation induction by arylamines and arylamides.

This publication has 47 references indexed in Scilit: