HDL3 and HDL2 determination by a combined ultracentrifugation and precipitation procedure

The aim of the present study was to evaluate a method to separate lipoproteins by ultracentrifugation simultaneously at density 1.006 and 1.125. This procedure combined with heparin-MnCl2 precipitation would facilitate the simultaneous determination of lipid levels of high density lipoproteins (HDL) and its main subfractions (HDL2 and HDL3, including very high density lipoproteins (VHDL)) and of very low (VLDL) and low density lipoprotein (LDL) fractions. Centrifugation at 105 500 X g (mean) for 24 h in a Beckman L5-50 ultracentrifuge with a Ti50 rotor seemed to give an adequate separation. The correlation coefficients for duplicate samples were 0.95 and 0.96 for HDL3-cholesterol and HDL3-phospholipids, respectively. The error of the method for HDL, HDL2 and HDL3 lipids was around half that of the intra-individual variation and comparable to the results for determination of conventional lipoprotein fractions. Therefore the suggested method seems applicable for evaluation of HDL2 and HDL3 levels in selected clinical material.