Visualization of the uptake of high-density lipoprotein by rat aortic endothelial cells and smooth muscle cells in vitro.

High-density lipoproteins (HDL) were conjugated to Fluorescein 1,1'-dioctadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI) or colloidal gold for the investigation of ultrastructural aspects of binding and uptake of HDL by cholesterol-loaded cultured endothelial and smooth muscle cells from rat aorta. When cells were incubated for 2 h at 4 degrees C, HDL-DiI and HDL-gold conjugates were seen only on the cell surface. When cells were returned to incubation at 37 degrees C for 5 min, HDL-DiI appeared in the cytoplasm and colocalized with the fluorescent cholesteryl ester tag BODIPY-FL-C12.