Preparative and quantitative isolation of plasma lipoproteins: rapid, single discontinuous density gradient ultracentrifugation in a vertical rotor.

A rapid method has been developed for separation of the major plasma lipoproteins from up to 96 ml of plasma by a single ultracentrifugation step. This separation was achieved by a discontinuous density gradient centrifugation between the density range of 1.006 and 1.30 g/ml in Sorvall vertical rotors. Each lipoprotein fraction was sharply banded with VLDL at the top, LDL in the upper middle, and HDL in the lower middle portion of the tube. Use of authentic 125I-labeled lipoproteins showed that complete separation of the three major classes and partial separation of HDL2 and HDL3 was achieved. The lipoprotein fractions prepared by this technique have properties indistinguishable from those isolated by the sequential flotation method in regard to their equilibrium banding density, electrophoretic mobility, and apolipoprotein composition. This method is suitable for the preparative isolation of lipoproteins as well as for quantitative clinical determinations of cholesterol and triglycerides in VLDL, LDL and HDL fractions of plasma. Used as an analytical tool this method allows samples as small as 1 ml of plasma and spin times as short as 45 min. Cholesterol levels in HDL fractions separated by this method have significantly lower values (P less than 0.05) than those estimated by the heparin-manganese chloride precipitation method.