Differences in processing of cholesterol between rat liver endothelial cells and rat peritoneal macrophages

Isolated rat liver endothelial cells and rat peritoneal macrophages were incubated with [3H]cholesteryl oleate labeled acetylated LDL in the presence of [14C]oleate in order to compare the fate of cholesteryl esters introduced into the cells by a so-called atherogenic lipoprotein. It was found that 5-times more [3H]cholesteryl oleate became associated with the endothelial cells per mg cell protein than with the macrophages. Hydrolysis of the cholesteryl esters proceeded in both cell types at a similar rate. In macrophages, however, the cholesterol formed is re-esterified at a 5-fold higher rate than in the liver endothelial cells. It is concluded that the cholesteryl esters introduced into the liver endothelial cells by acetylated LDL are rapidly hydrolysed and only to a very limited extent reconverted to cholesteryl esters, which contrasts the fate of this substrate with peritoneal macrophages. This property may allow the endothelial liver cells to function as a proper protection system against circulating atherogenic lipoproteins.