The Lipid Composition of Human Plasma Chylomicrons.

The lipid composition of human chylomicrons has been studied using blood collected from normal male volunteers after ingestion of 200 g of butter fat. The concentration of chylomicrons in the blood samples varied widely among 12 subjects but in each case the following lipids were present : triglycerides, diglycerides (probably the 1,2-isomers), monoglycerides, free and esterified cholesterol, traces of free fatty acids, phosphatidyl ethanolamine, phosphatidyl choline, sphingomyelin (two components), and lysolecithin. The fatty acid composition of chylomicron triglycerides was usually similar to that of butter, but myristic and shorter-chain acids showed concentrations lower than those in butter. Pooled phospholipids were fractionated by preparative thinlayer chromatography. Phosphorus determinations indicated the following proportions of components (mole per cent of total phospholipids) : phosphatidyl ethanolamine region, 6y0 ; phosphatidyl choline, 79% ; sphingomyelins, 12% ; lysolecithin, 4%. The fatty acid compositions of the chylomicron phospholipids have been determined. The total sphingomyelin region contained C22, Cza, Cz4, and C24 monoenoic acids as major components.