DISTRIBUTION OF CHOLESTEROL AND APOLIPOPROTEIN-A-L AND APOLIPOPROTEIN-A-LL IN HUMAN HIGH-DENSITY LIPOPROTEIN SUBFRACTIONS SEPARATED BY CSCL EQUILIBRIUM GRADIENT CENTRIFUGATION - EVIDENCE FOR HDL-SUBPOPULATIONS WITH DIFFERING A-L-A-LL MOLAR RATIOS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 20  (2) , 200-207
Abstract
High density lipoproteins (HDL) were characterized as a function of hydrated density. HDL was subfractionated on the basis of hydrated density by CsCl density gradient centrifugation of whole serum or the d (density) 1.063-1.25 g/ml HDL fraction isolated from 3 men and 3 women. Apolipoprotein A-I and A-II quantitation by radial immunodiffusion showed that the A-I/A-II ratio varied with the lipoprotein hydrated density. The A-I/A-II molar ratio of HDL lipoproteins banding between d 1.106-1.150 g/ml was nearly constant at 2.2 .+-. 0.2. In the density range 1.151-1.25 g/ml the A-I/A-II ratio increased as the density increased. In the density range between 1.077-1.105 the A-I/A-II ratio increased as the density decreased, ranging from 2.8 .+-. 0.5 for the d 1.093-1.105 g/ml fraction to 5.6 .+-. 1.3 for the d 1.077-1.082 g/ml fraction. The d 1.063-1.076 g/ml fraction and the d 1.077-1.082 g/ml fractions had comparable A-I/A-II ratios. Serum and the d 1.063-1.25 g/ml HDL fraction exhibited similar trends. The cholesterol/(A-I + A-II) ratio decreased as the density increased in all 12 samples (6 serum and 6 HDL) examined. Gradient gel electrophoresis of the density gradient fractions showed that as the density increased from 1.063 to 1.200 g/ml the apparent MW decreased from 3.9 .times. 105 to 1.1 .times. 105. HDL subfractions with the same hydrated densities had comparable MW and A-I/A-II and cholesterol/(A-I + A-II) ratios when isolated from men and women. HDL contains subpopulations that differ in the A-I/A-II molar ratio.