Recovery of cholesterol and triacylglycerol in very-fast ultracentrifugation of human lipoproteins in a large range of concentrations

Abstract

Very-fast ultracentrifugation using a benchtop ultracentrifuge was applied to the analysis of lipoproteins in 0.5 ml of human plasma. VLDL, IDL and LDL were flotated at densities of 1.006, 1.019 and 1.063 kg/l in runs lasting 30, 100 and 100 minutes. Chylomicrons, if present, were flotated in a separate run. HDL were isolated by precipitation of the apolipoprotein B-containing lipoproteins from total plasma using polyethylene glycol. Three series of separations were routinely performed: 1. VLDL run alone (632 samples), 2. VLDL run + LDL run (122 samples), and 3. Chylomicron separation + VLDL run + IDL run (92 samples). The concentrations of cholesterol and triacylglycerol were obtained for plasma, chylomicrons, VLDL, IDL, LDL and HDL. Plasma values ranged from 1.8 to 37.1 mmol/l cholesterol and 0.26 to 50.2 mmol/l triacylglycerol. The plasma triacylglycerol concentrations were corrected for free glycerol by 3% (for triacylglycerols < 2.5 mmol/l) and by 2% (for triacylglycerols > or = 2.5 mmol/l). The recovery rate of lipids after ultracentrifugation was determined by comparing the concentrations in lipoproteins and in plasma. It was near to 100% and decreased for samples with extremely high lipid concentrations.