title: Factors affecting resistance of low density lipoproteins to oxidation.
abstract: Oxidation resistance (OR) of low density lipoproteins (LDL) is frequently determined by the conjugated diene (CD) assay, in which isolated LDL is exposed to CU2+ as prooxidant in the range of 1-10 microM. A brief review on major findings obtained with this assay will be given. A consistent observation is that vitamin E supplements or oleic acid-rich diets increase OR. Oxidation indices measured by the CD assay and effects of antioxidants very significantly depended on the Cu2+ concentration used for LDL oxidation. For medium and high Cu2+ concentrations, the relationship between lag time and propagation rate can be described by a simple hyperbolic saturation function, which has the same mathematical form as the Michaelis-Menten equation. At medium and high Cu2+ concentrations (0.5 to 5 microM), vitamin E increases lag time in a dose-dependent manner. The increase is higher for 0.5 microM Cu2+ as compared to 5 microM. At low Cu2+ concentrations (0.5 microM or less), the mechanism of LDL oxidation changes. Significant oxidation occurs in a preoxidation phase, which commences shortly after addition of Cu2+. Preoxidation is not inhibited by vitamin E. It is concluded that much additional work is needed to validate the importance of oxidation indices derived from CD and similar assays.
authors.affiliation: Institute of Biochemistry, University of Graz, Austria.
authors.forename: O
authors.initials: O
authors.lastname: Ziouzenkova
authors.forename: S P
authors.initials: SP
authors.lastname: Gieseg
authors.forename: P
authors.initials: P
authors.lastname: Ramos
authors.forename: H
authors.initials: H
authors.lastname: Esterbauer
mesh_terms: D000975:Antioxidants / Q000494:pharmacology*; D003300:Copper / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008077:Lipoproteins, LDL / Q000378:metabolism*; D010084:Oxidation-Reduction; D014810:Vitamin E / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D008077:Lipoproteins, LDL; D014810:Vitamin E; D003300:Copper