MEASUREMENT OF CHOLESTEROL ESTER HYDROPEROXIDES OF HIGH AND COMBINED LOW AND VERY-LOW-DENSITY LIPOPROTEIN IN HUMAN PLASMA

The cholesterol ester (CE) hydroperoxides (HPO) were measured in high density lipoprotein (HDL) and combined low and very low density lipoproteins (LDL+VLDL) by a high pressure liquid chromatography with a post column detection system using diphenyl-1-pyrenylphosphine. Human plasma lipoproteins were fractionated from 2 ml of plasma with dextran sulfate and Mg2+ to each fraction from which CE-HPO was extracted with n-hexane,. The fractionation had no influence on the CE-HPO values in a sample. The relative standard deviations of the CE -HPO were 5.4% (n=6) from the HDL fraction and 4.8% (n=5) from the LDL+VLDL fraction. The CE-HPO) were 6.8+/-2.6 nM (in HDL) and 20.0+/-5.6 nM (in LDL+VLDL) from 10 fresh human plasma samples. The method was used to follow the increase and decrease of CE-HPO in each lipoprotein fraction by the incubation of fresh plasma spiked with dilinoleoyl phosphatidylcholine hydroperoxide.