title: Mitochondria and microsomal membranes have a free radical reductase activity that prevents chromanoxyl radical accumulation.
abstract: Enzyme-dependent mechanisms which prevent accumulation of chromanoxyl radicals derived from the vitamin E analogue, 2,2,5,7,8-pentamethyl-6-hydroxycromane (PMC), were characterized in rat liver microsomal and mitochondrial membranes. The free radical oxidation product of PMC (chromanoxyl radical) was generated in membranes using either photochemical (uv light) or enzymatic (lipoxygenase and arachidonic acid) methods and detected by ESR. Substrates (NADH or NADPH) prevented accumulation of chromanoxyl radicals until the substrate was fully consumed. In microsomes, reduced glutathione increased the efficacy of NADPH in preventing the accumulation of the chromanoxyl radical, but was without effect in the absence of NADPH. Ascorbate also prevented accumulation of the chromanoxyl radical. It is concluded that rat liver microsomes and mitochondria have both enzymatic and non-enzymatic mechanisms for reducing chromanoxyl radicals.
authors.affiliation: Applied Science Division, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
authors.forename: L
authors.initials: L
authors.lastname: Packer
authors.forename: J J
authors.initials: JJ
authors.lastname: Maguire
authors.forename: R J
authors.initials: RJ
authors.lastname: Mehlhorn
authors.forename: E
authors.initials: E
authors.lastname: Serbinova
authors.forename: V E
authors.initials: VE
authors.lastname: Kagan
mesh_terms: D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism; D001205:Ascorbic Acid / Q000494:pharmacology; D001578:Benzopyrans / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D002839:Chromans / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D005978:Glutathione / Q000494:pharmacology; D008081:Liposomes / Q000378:metabolism; D008084:Lipoxygenase / Q000378:metabolism; D008862:Microsomes, Liver / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000201:enzymology*; D009243:NAD / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010777:Photochemistry; D051381:Rats; D013367:Submitochondrial Particles / Q000378:metabolism; D014466:Ultraviolet Rays; D014810:Vitamin E / Q000378:metabolism
chemical_list: D001095:Arachidonic Acids; D001578:Benzopyrans; D002839:Chromans; D005609:Free Radicals; D008081:Liposomes; D009243:NAD; D014810:Vitamin E; D016718:Arachidonic Acid; D009249:NADP; C029141:2,2,5,7,8-pentamethyl-1-hydroxychroman; D010088:Oxidoreductases; D008084:Lipoxygenase; D005978:Glutathione; D001205:Ascorbic Acid