linoleic-acid and benzidine

4-Aminobyphenyl (4-Ab), benzidine (Bz), and Bz congeners were evaluated for their ability to induce genotoxicity through an oxidative mechanism. The mutagenicity of these compounds was tested in the presence and absence of Aroclor 1254-induced rat S9 mix using Salmonella typhimurium tester strain TA102, which is sensitive to agents producing reactive oxygen species (ROS). In the presence of S9, 4-Ab, Bz, N-acetyl-benzidine, and 3,3-dimethoxybenzidine were strongly mutagenic in TA102, whereas, 3,3,5,5-tetra-methylbenzidine, 3,3-dimethylbenzidine (O-tolidine), and N,N-diacetylbenzidine were not mutagenic. In addition, 3,3-dichlorobenzidine and 4,4-dinitro-2-biphenylamine were directly mutagenic in TA102. Incorporation of the free radical and metal scavengers, catalase, superoxide dismutase (SOD), butylated hydroxytolune (BHT), and ethylenediamine tetraacetic acid (EDTA) reduced the mutagenic responses of 4-Ab and Bz, whereas heat-inactivated catalase and SOD had no effect. 4-Ab and Bz also induced lipid peroxidation in the presence of S9 mix as shown using the thiobarbituric acid reactive substances assay. The results of this study indicate that 4-Ab and Bz induce mutations through the induction of ROS.

Topics: 3,3'-Dichlorobenzidine; Aminobiphenyl Compounds; Animals; Benzidines; Butylated Hydroxytoluene; Catalase; Dianisidine; Edetic Acid; Linoleic Acid; Lipid Peroxidation; Liver; Models, Biological; Molecular Structure; Mutagenicity Tests; Rats; Reactive Oxygen Species; Salmonella typhimurium; Superoxide Dismutase

The evidence presented here constitutes the first report on the occurrence of lipoxygenase (LO) activity in the adult human liver. LO activity was isolated free of hemoglobin from the whole liver cytosol by affinity chromatography using a concanavalin-A sepharose 4B column, and some properties of its dioxygenase and co-oxidase activities were examined. High-pressure liquid chromatography (HPLC) analyses of arachidonic acid metabolites suggested the presence of 5-, 12-, and 15-LO activities in the human liver. Linoleic acid was converted into 13-hydroperoxyoctadecadienoic acid. The dioxygenase activity with a Vmax value of 1.74 mumoles/min/mg protein and a Km value of 0.48 mM was noted in the presence of different concentrations of linoleic acid at pH 10. The activity was markedly stimulated by the presence of calcium, ATP, hydrogen peroxide, and KCl in the assay medium. Under optimum conditions, all the xenobiotics tested were cooxidized by the enzyme preparations in the presence of linoleic acid. Kinetic data obtained for benzidine oxidation yielded a Km value of 0.53 mM and a Vmax value of 90.9 nmoles/min/mg protein. At present, the significance of these findings in in vivo toxicity of benzidine is unknown. The linoleic acid-dependent dioxygenase and co-oxidase activities were thermolabile and inhibited by micromolar concentrations of several classical LO inhibitors, further confirming the involvement of LO in these reactions.

Topics: Adenosine Triphosphate; Adult; Arachidonic Acid; Benzidines; Calcium; Chromatography, Affinity; Chromatography, High Pressure Liquid; Concanavalin A; Cytosol; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors; Female; Hemoglobins; Humans; Hydrogen Peroxide; Hydrogen-Ion Concentration; Linoleic Acid; Linoleic Acids; Lipoxygenase; Liver; Male; Middle Aged; Oxidation-Reduction; Potassium Chloride; Xenobiotics