It is well-known that high-density lipoprotein (HDL) mediates the transport of cholesterol from peripheral tissues to liver through “reverse cholesterol transport” for metabolism. However there is considerable debate about the mechanisms by which HDL removes excess cholesterol from cells. Two different pathways have been suggested: (i) a docking receptor promots cholesterol translocation, or (ii) a receptor mediates intracellular endosomal pathway termed “retroendocytosis“. Our previous studies have indicated that the removal of cholesterol from aortic endothelial and smooth muscle cells in the presence of HDL is facilitated by plasmalemmal vesicles. in this study, our emphasis is on the ultrastructural changes of cholesterol-loaded endothelial cells after incubated with HDL at different time intervals. Furthermore, the mechanism of HDL-mediated cholesterol efflux by cultured aortic endothelial cells is investigated by immunoelectrophoresis.

Confluent monolayers of endothelial cells were incubated in cholesterol DMEM medium for 48 hr.