Phospholipids as modulators of hepatic recognition of chylomicron remnants. Observations with emulsified lipoprotein lipids.

The lipids extracted from chylomicrons, chylomicron remnants generated in vivo and hepatic-lipase-treated chylomicrons were emulsified by sonication. These emulsified particles retained the capacity of the native lipoproteins to be differentiated by the liver in vivo, i.e. only the particles derived from remnant and hepatic-lipase-treated chylomicron lipids were efficiently taken up by the liver. To investigate the role of phospholipids in this differentiation process, the phospholipids of all three lipoprotein preparations were separated from the remaining lipids by silicic acid chromatography. The phospholipid-free lipid fraction of chylomicrons was then emulsified with the phospholipids derived from each of the three lipoprotein preparations. Only the particles emulsified with phospholipids derived from remnants and hepatic-lipase-treated chylomicrons were efficiently taken up by the liver in vivo. These results support the proposition that phospholipids modulate the hepatic differentiation between chylomicrons and remnants in vivo.