Simple and specific test for measuring lipid peroxides in plasma

The specificity of an iodometric assay for measuring lipid peroxides in lipoproteins was tested, compared with the fluorimetric thiobarbituric acid assay, and adopted for detecting lipid peroxide in plasma samples. Oxidation of low density lipoproteins in vitro by Cu2+, lipoxidase, and phagocytosing polymorphonuclear leucocytes was sensitively detected by the iodometric assay. Unlike the thiobarbituric acid assay, neither non-lipid substances commonly present in plasma, nor platelet or polymorphonuclear leucocyte by-products interfered with the iodometric assay. The iodometric assay measured a normal mean (SD) plasma lipid peroxide concentration of 10.8 (2.1) microM; n = 63. Two weeks after the start of a high cholesterol diet in rabbits (n = 5), a sixfold increase in plasma lipid peroxide concentrations was measured by iodometric assay. The specificity of a simple and sensitive iodometric test of lipid peroxidation was superior to that of the thiobarbituric acid assay. This iodometric assay should therefore provide a much more accurate assessment of lipid peroxide in plasma samples.