Inhibition of rat hepatic sterol formation from squalene by plasma lipoproteins

The conversion of 3H-squalene to sterols by rat liver microsomes and cytosol was inhibited by individual rat and human plasma lipoproteins at various concentrations. This inhibition was also observed with added human high density apolipoprotein, but triglycerides, cholesterol, or cholesteryl esters had no inhibitory effects. Lipoproteins and apo high density lipoprotein (HDL) were demonstrated to bind 3H-squalene in vitro. The binding of 3H-squalene by apo HDL could be reversed by increasing concentration of liver cytosol containing sterol carrier protein.