title: In vivo detection of aflatoxin-induced lipid free radicals in rat bile.
abstract: Aflatoxin B1 (AFB1), a potent hepatotoxin and hepatocarcinogen, is metabolized in the liver via cytochrome P-450 to an AFB1-8,9-epoxide intermediate. The formation of the AFB1-8,9-epoxide correlates with the pathological changes observed in numerous mammalian species. Oxidative damage has been postulated to play a major role in the mechanisms associated with AFB1-induced cytotoxicity and carcinogenecity in mammalian species. The aim of this study was to detect and identify free radical intermediates from the hepatic metabolism of AFB1 in vivo. Rat bile ducts were cannulated and rats were treated simultaneously with AFB1 (3 mg/kg i.p.) and the spin trapping agent 4-POBN (alpha-(4-pyridyl-1-oxide)-N-tert-butyl nitrone) (1 g/kg i.p.), and bile was collected over a period of 2 h at 20-min intervals. ESR spectroscopy was used to detect a carbon-centered radical adduct of 4-POBN in rat bile. The effect of metabolic inhibitors, such as deferoxamine mesylate (DFO), an iron chelator, and SKF 525A, a cytochrome P-450 inhibitor, on in vivo aflatoxin-induced free radical formation were also studied. It was found that there was a significant decrease in free radical formation by pre-treatment with both DFO and SKF 525A. This indicates that oxidation of AFB1 generates free radical species via CYP metabolism and an iron-mediated redox mechanism.
authors.affiliation: North Queensland Magnetic Resonance Centre and Department of Physiology and Pharmacology, School of Biomedical Sciences, Molecular Sciences Building, James Cook University, Townsville 4811 Queensland, Australia. Rheal.Towner@jcu.edu.au
authors.forename: R A
authors.initials: RA
authors.lastname: Towner
authors.forename: R P
authors.initials: RP
authors.lastname: Mason
authors.forename: L A
authors.initials: LA
authors.lastname: Reinke
mesh_terms: D016604:Aflatoxin B1 / Q000008:administration & dosage / Q000378:metabolism*; D000818:Animals; D001646:Bile / Q000737:chemistry / Q000378:metabolism*; D003676:Deferoxamine / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005609:Free Radicals / Q000032:analysis*; D007502:Iron Chelating Agents / Q000494:pharmacology; D008055:Lipids / Q000032:analysis*; D008070:Lipopolysaccharides; D008099:Liver / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D009589:Nitrogen Oxides / Q000008:administration & dosage / Q000032:analysis / Q000652:urine; D011335:Proadifen / Q000494:pharmacology; D011725:Pyridines; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011916:Rats, Inbred F344; D019097:Spin Trapping
chemical_list: D004791:Enzyme Inhibitors; D005609:Free Radicals; D007502:Iron Chelating Agents; D008055:Lipids; D008070:Lipopolysaccharides; D009589:Nitrogen Oxides; D011725:Pyridines; D012333:RNA, Messenger; C043438:alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone; D016604:Aflatoxin B1; D011335:Proadifen; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D003676:Deferoxamine