Preparation of high-density lipoproteins labelled exclusively at the cholesteryl ester moiety

The in vitro preparation of HDL radiolabelled at the cholesteryl ester moiety was determined by incubating different serum fractions with [3H]cholesteryl linoleate or cholesteryl [14C]oleate dissolved in dimethylsulfoxide (DMSO) and subsequent re-isolation of HDL from the incubation mixture by ultracentrifugation. Using the supernatant obtained by precipitation of apolipoprotein B-containing lipoproteins with phosphotungstate/MgCl2 or using the greater than 1.075 kg/l fraction of sera, the bulk of the added radioactivity could be recovered in the re-isolated HDL fraction, as demonstrated by density gradient ultracentrifugation or by gel chromatography. Incubation experiments using whole sera or the greater than 1.063 kg/l fraction of sera resulted in the preferential association of the labelled cholesteryl linoleate with apolipoprotein B-containing lipoproteins.