Molecular Pharmacology, Vol 14, 682-692, Copyright © 1978 by the American Society for Pharmacology and Experimental Therapeutics

Mutagenic Activation of N-Hydroxy-2-acetylaminofluorene in the Salmonella Test System: the Role of Deacetylation by Liver and Kidney Fractions from Mouse and Rat

¹ Biochemical Pharmacology Section, Laboratory of Chemical Pharmacology, Developmental Therapeutics Program, Division of Cancer Treatment, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20014

The Ames bacterial mutagenesis system was used to evaluate the role of the deacetylase and sulfotransferase in the mutagenic activation of N-hydroxy-2-acetylaminofluorene. The mutagenicity of N-hydroxy-2-acetylaminofluorene mediated by liver or kidney microsomes was independent of treatment of mice or rats with microsomal enzyme inducers and, at equivalent protein concentrations, was the same whether mouse liver or mouse kidney microsomes were used. N-Hydroxy-2-acetylaminofluorene mutagenesis with mouse and rat liver or kidney microsomes was completely inhibited by 0.1 mM paraoxon and partially inhibited by addition of 3'-phosphoadenosine 5'-phosphosulfate when rat liver 9000 x g supernatant was used. Although the rates of deacetylation of 2-acetylaminofluorene and N-hydroxy-2-acetylaminofluorene in vitro were lower in kidney microsomes than in liver microsomes of either the mouse or the rat, both reactions were also completely inhibited by 0.1 mM paraoxon. The addition of ascorbic acid (10 mM) approximately doubled the mutagenicity of N-hydroxy-2-acetylaminofluorene in the presence of mouse kidney microsomes but had no effect on the mutagenicity of N-hydroxy-2-aminofluorene in the absence of microsomal protein. Butylated hydroxytoluene (10 mM) had very little or no effect, in either the absence or presence of 10 mM ascorbic acid, on the mutagenicity of N-hydroxy-2-acetylaminofluorene with liver or kidney microsomes. Our data indicate that deacetylation is the most important step in the mutagenic activation of N-hydroxy-2-acetylaminofluorene by mouse and rat liver and kidney fractions and that the arylnitrenium ion, rather than the nitroxyl free radical, is the electrophilic species interacting with the bacterial DNA, resulting in the frameshift mutation.

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ACKNOWLEDGMENT The authors appreciate the fine secretarial assistance of Mrs. Katherine Brungardt.