Fractionation of Plasma Lipoproteins by Density Gradient Centrifugation in Swing-out Rotors

Abstract

1. A density gradient flotation procedure for fractionation of plasma lipoproteins is described. The present method was tested for fractionation of plasma lipoproteins of man, rat, dog, rabbit, mouse, and guinea-pig. 2. After adjustment of the density of plasma samples to 1.250 they were overlayered with a stepwise NaCl-KBr-gradient (density 1.210–1.006) in a preparative centrifuge tube. 3. After 5-h centrifugation (66,000–94,000 × g) in a swing-out rotor, the very low density (VLDL) and low density (LDL) lipoproteins were well resolved from each other in samples of all species studied, whereas the high density lipoproteins (HDL) remained at the bottom of the tube together with the other plasma proteins. After 24-h centrifugation, the HDL fractions of rat, mouse, and dog had started to separate from the bulk of other proteins. During the 24-h centrifugation, however, the VLDL and LDL fractions had floated to the top of the tube and separation of the two was not possible in samples of any species. 4. When the lipoproteins were prc-purified by flotation at a density of 1.230, distinct fractions representing VLDL, LDL, and HDL, respectively, were obtained during subsequent 5-h density gradient centrifugations under the above conditions.

Key Words:

• Centrifugation
• zonal
• cholesterol
• lipids
• phospholipids
• proteins
• ultracentrifugation