Study of nonspecific internalization of cholesteryl esters by hepatoma HepG2 cells

Cholesteryl oleate - POPC dispersion (1 : 3, mol/mol, mean particle size of 110 +/- 20 nm) was taken up by human hepatoma Hep G2 dells via endocytosis . The dispersion-associated cholesteryl oleate was shown to be internalized by Hep G2 cells in a time- and concentration-dependent mode. The total upt ake and internalization of cholesteryl oleate (at a cholesteryl oleate conc entration in a medium of 100 mu M) were 1.5 nmol and 0.8 nmol cholesteryl o leate/mg of cell protein/24h, respectively. The intracellular cleavage of e xogenous cholesteryl oleate led to free cholesterol capable to dissociate f rom cells into medium and to metabolize to polar water-soluble products and oleic acid, which was involved in triacylglycerols biosynthesis. The LDL r eceptors in cells do not take part in endocytosis and internalization of li pid dispersion; the presence of the cholesteryl oleate - POPC dispersion do es not affect receptor-dependent internalization of LDL-associated choleste ryl eaters in Hep G2 cells. The data obtained allowed to speculate that non specific internalization of cholesteryl esters by hepatocytes is a substant ial part of nonpolar lipid clearance.