A correlation between the carcinogenicity of isomeric N-hydroxy-N-acetylaminofluorenes and their in vitro effect on mitochondria.

While 3 parent carcinogens, namely AAF-2,2 dibenz (a,h) anthracene, and N-acetyl-4-aminobiphenyl3 did not expose a mitochondrial thiol group, appropriate acidic metabolites of these carcinogens did expose a mitochondrial thiol group (6, 7, 9). In orderto examine thisconfluence further, we have experimented with AAF-2 and some of its isomers, namely, N-OH-AAF4, have also been examined (Chart 1). In this report, the behaviors of these 2 sets of isomers in the in vitro mitochondrial systems (derived from rat liver) have been compared with the carcinogenicity [in the rat (2)] of the isomeric hydroxamic acids. These compounds are considered isomeric proximate carcinogens derived from the aryl amides by either metabolic or synthetic hydroxylation (2). MATERIALS AND METHODS General procedures, methods, and purification of the water have been described previously for the mitochondrial volume change experiments (9, 10). The pH of the Tris chloride buffer is indicated on the charts. Incubation was at 27°in standard rectangular glass cuvets with a 1-cm light path. The basic reaction mixture for the volume change experiments had a final volume of 3 ml and contained 0.75 mg mitochondrial protein (prepared from rat liver), 75 mM sucrose, and 75 mM Tris chloride buffer. The supplier of the rats was The Holtzman Co., Madison, Wis. A decrease in absorbance at 520 nM was taken as a measure of mitochondrial swelling. A Model was used. All cations were added in the form of chloride salts, and anions were added in the form of Tris salts neutralized to pH 7.4. Solutions of the 4 aryl amides and the 4 hydroxamic acids 2 The abbreviations used are: AAF-2, N-acetyl-2-aminofluorene;