Effect of core composition and particle size of lipid emulsions on apolipoprotein transfer of plasma lipoproteins in vivo.

Lipid emulsions corresponding in size and surface composition to chylomicron and low density lipoprotein but differing in lipid core composition were injected into rats a tail vein cannula and 10 min later blood was withdrawn via the abdominal aorta. Plasma lipoproteins were isolated by ultracentrifugation and the lipid and apolipoprotein composition was determined by gas-liquid chromatography and gel electrophoresis, respectively. It was found that apolipoprotein C peptides were transferred to Sf greater than 400 particles of large diameter regardless of whether their cores contained cholesteryl esters or triacylglycerols, but not to Sf greater than 400 particles of small diameter. Apolipoprotein A-I transferred to both large and small diameter cholesteryl ester core particles but only to larger diameter triacylglycerol core particles. In contrast, apolipoprotein E became associated with small and large diameter particles regardless of core composition. In addition, all Sf greater than 400 fractions contained significant amounts of apopeptides with molecular weights greater than 45 000, which did not correspond to the common apolipoproteins. This is the first study to prove systematically the effects of lipid composition and particle size on apolipoprotein transfer in vivo.