Dehydroxylation and deacetylation of N-hydroxy- N-2-fluorenylacetamide by rat liver and brain homogenates

Abstract

Two reactions, dehydroxylation and deacetylation of the proximate carcinogen N-hydroxy- N-2-fluorenylacetamide were studied with liver and brain homogenates, or with a soluble fraction from liver of young or adult male or female rats of two strains. Incubation of N-hydroxy- N-2-[9- 14 C]fluorenylacetamide with tissue homogenate in 0.2 M Tris buffer (pH 8.1) gave progressively decreasing levels of substrate. The products, N-2-fluorenylacetamide and 2-fluorenamine, were resolved and identified by solvent partition, paper chromatography, ultraviolet spectroscopy, and color tests. Liver homogenate from 2 rat strains was most active, the soluble liver fraction slightly less so, and brain homogenate least. Deacetylation was but dehyroxylation was not inhibited by 0.1 M fluoride. Both reactions proceeded equally well in nitrogen or in air. The dehydroxylase was inactive after 1 h at 37°. The decaylase was somewhat more stable. Linear increases in protein-binding of 14C from the substrate were found. The final level was lower in liver from adult female rats than from males, but was similar with weanling rats. Binding was inhibited somewhat by fluoride and more so by a nitrogen atmosphere. Some of the binding may have been due to the oxidation of amine or hydroxylamine in the presence of tissue. Isotope from synthetic N-2-[ 14C] fluorenylhydroxylamine and 2-nitroso[9 −14C]fluorene bound to serum proteins, liver homogenate or soluble liver fractions, hemoglobin, albumin, γ-globulin, or histones. 2-Nitrosofluorene reacted similarly in air and in nitrogen. It may be the active intermediate.