Binding of benzo(a)pyrene to hepatic cytosolic protein enhances its microsomal oxidation.
Dixit-R; Bickers-DR; Mukhtar-H
Biochem Biophys Res Commun 1982 Feb; 104(3):1093-1101
Evidence was presented to indicate that the binding of benzo(a)pyrene (50328) (BaP) to a protein in rat liver cytosol facilitates its oxidation by microsomal enzymes. Cytosols were prepared from male Sprague-Dawley-rats. Sephadex G-100 gel permeation chromatography of rat liver cytosol saturated with carbon- 14 labeled BaP resulted in two peaks of protein bound radioactivity. Glutathione-S-transferase (GST) activity toward 1-chloro-2,4- dinitrobenzene as substrate was eluted as a single major peak which coincided with one peak of protein bound BaP. Oxidation of protein bound BaP, GST rich fractions, by microsomes from control or 3- methylcholanthrene treated rats was significantly enhanced as compared to ethanol suspended BP. The formation of oxidized products from the protein bound BaP was dependent on incubation time and microsomal protein concentration, required NADPH and was inhibited by monooxygenase inhibitors alpha-napthoflavone, 1-benzylimidazole, metyrapone and SKF-525A. Coemergence of BaP binding protein with GST suggests that the soluble protein could be one of the glutathione-S-transferases.
NIOSH-Publication; NIOSH-Grant; Dermatitis; Liver-enzymes; Enzyme-activity; Metabolic-study; Pyrenes; Lipids; Carcinogens; Liver-microsomes
Medicine Cleveland V a Hospital 10701 East Blvd Cleveland, Ohio 44106
Biochemical and Biophysical Research Communications
Case Western Reserve University, Cleveland, Ohio