THE PHOSPHOLIPID COMPOSITION OF HUMAN SERUM LIPOPROTEIN FRACTIONS SEPARATED BY ULTRACENTRIFUGATION*

Abstract

Serum lipoprotein fractions of density < 1.019, 1.019 to 1.063, and > 1.063 from an apparently healthy nonfasting adult male were separated by ultracentrifugation and analyzed for the individual phospholipids using chromatography on both silicic acid columns and paper. All of the phospholipids and possible phospholipid constituents identified were found in each of the 3 fractions. Serum lipoprotein fractions of density < 1.019, < 1.063 and < 1.063 from 8 apparently healthy fasting adults were separated by ultracentrifugation and analyzed for the individual phospholipids, cholesterol, cholesterol ester and triglyceride, using chromatography on silicic acid columns. The relative proportions of the individual phospholipids in the fractions with density < 1.019 and < 1.063 were similar but differed from the values found in the fraction with density > 1.063. In the fraction with density < 1.063, the molar ratio of sphingomyelin-to-lecithin was twice, and "cephalin"-to- sphingomyelin about 1/2, the corresponding value found in the fraction with density > 1.063. Both fractions, theerfore, had similar molar "cephalin" -to-lecithin ratios. The molar lysolecithin-to-lecithin ratio of the heavier fraction was almost 3 times that of the lighter fraction, but there was much variation between subjects.