title: Temporal relationships between the loss of vitamin E, protein sulfhydryls and lipid peroxidation in microsomes challenged with different prooxidants.
abstract: Microsomal membranes exposed to various prooxidants displayed distinct patterns in the temporal relationships between the loss of antioxidants and the onset of lipid peroxidation. Prooxidants included ADP-chelated iron with reductants (NADPH and ascorbate), or compounds that generate peroxyl radicals (tert-butyl hydroperoxide and 2,2'-azobis(2-amidinopropane)), or free metal ions (Fe2+ and Cu2+). Lipid peroxidation initiated by Fe2+ began simultaneously with the loss of alpha-tocopherol, while about 15% of alpha-tocopherol was lost during the lag phase preceding lipid peroxidation in systems containing chelated iron. A substantial depletion of alpha-tocopherol (49-69%) preceded peroxidation when initiated by peroxyl radicals, while 97% of the antioxidant disappeared preceding peroxidation initiated by copper. The loss of protein sulfhydryl groups also varied between the prooxidants (ranging from 0 to 82% loss prior to the onset of peroxidation) to a degree that roughly paralleled the loss of vitamin E. Therefore, important determinants of peroxidation are prooxidant-dependent, and not only include alpha-tocopherol and sulfhydryl groups, but also membrane integrity, propagation reactions and the availability of catalytic transition metals.
authors.affiliation: Institut für Physiologische Chemie I, Universität Düsseldorf, F.R.G.
authors.forename: A
authors.initials: A
authors.lastname: Scheschonka
authors.forename: M E
authors.initials: ME
authors.lastname: Murphy
authors.forename: H
authors.initials: H
authors.lastname: Sies
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D003300:Copper / Q000378:metabolism; D019327:Copper Sulfate; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D015227:Lipid Peroxidation; D008315:Malondialdehyde / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism*; D010083:Oxidants, Photochemical; D010084:Oxidation-Reduction; D013438:Sulfhydryl Compounds / Q000378:metabolism*; D014810:Vitamin E / Q000378:metabolism*
chemical_list: D010083:Oxidants, Photochemical; D013438:Sulfhydryl Compounds; D014810:Vitamin E; D008315:Malondialdehyde; D003300:Copper; D007501:Iron; D019327:Copper Sulfate