INTERACTION BETWEEN UNILAMELLAR EGG-YOLK LECITHIN VESICLES AND HUMAN HIGH-DENSITY LIPOPROTEIN

The interaction between unilamellar egg yolk lecithin vesicles and human plasma lipoproteins was studied in vitro as a model system for examining the mechanisms by which vesicles are modified in plasma. Vesicles were prepared by sonication and contained radiolabeled lecithin and small amounts of labeled cholesteryl oleate. Following incubation with plasma at 37 °C the vesicle-associated lipids eluted from Sepharose 4B columns as a smaller particle, similar in size to high density lipoprotein (HDL), and were isolated in the same density range as HDL by ultracentrifugation. A similar transformation occurred following incubation with HDL or apoHDL, but not when vesicles were incubated with purified very low or low density lipoprotein. Detailed studies of the interaction between HDL and vesicles indicated the rate of transformation to be temperature dependent and influenced by the relative concentration of reactants. Cholesteryl oleate was transferred from vesicles to the smaller particle more rapidly than lecithin. Chemical analysis of phospholipid in column eluates indicated complete transformation under optimized conditions, thereby excluding an exchange phenomenon. Protein was found to associate with vesicles during the transformation process. The transfer of lipids from unilamellar vesicles to an HDL-like particle suggests that analogous mechanisms for the mobilization of lipoprotein or membrane-associated lipids may occur in biological systems. © 1979, American Chemical Society. All rights reserved.