A RAPID METHOD FOR MEASUREMENT OF THE SUSCEPTIBILITY TO OXIDATION OF LOW-DENSITY-LIPOPROTEIN

Oxidation of low-density lipoprotein (LDL) may be important in the pat hogenesis of atherosclerosis. We describe a method which measures the oxidation resistance of LDL isolated by a rapid procedure without adde d antioxidants. LDL was isolated from heparinized plasma by density gr adient ultracentrifugation and desalted by gel filtration. The protein concentration was standardized to 50 mg/L and oxidation was promoted by copper (2 mu mol/L) at 37 degrees C. The total sample preparation t ime was 2.5 h. Conjugated diene production was monitored at lambda = 2 34 nm with computation of the lag time. LDL oxidation was inhibited by EDTA but not heparin. Albumin inhibited LDL oxidation but only in con centrations greater than 50 mg/L. LDL was stable in frozen plasma (- 7 0 degrees C) for 10 weeks, but unstable in the isolated and desalted s tate. The lag time for LDL from patients treated with the antioxidant probucol was markedly prolonged compared to normal subjects.