Free cholesterol distribution during in vitro lipolysis of rat plasma very low density lipoprotein: lack of a role for blood and heart cells

Abstract. In the present study, an attempt was made to quantify free cholesterol transfer from lipolyzed VLDL to HDL, blood cells and heart cells. The experiments were carried out in vitro or in the isolated perfused rat heart with rat plasma VLDL labelled biosynthetically with [¹⁴C]-palmitic acid and [³H]cholesterol, and with bovine milk lipoprotein lipase, human blood cells (erythrocytes, leucocytes and platelets) or rat plasma HDL. Exchange and transfer of free cholesterol was followed by radioactivity and specific activity determinations. The study demonstrated an exchange of free cholesterol between VLDL and blood cells (6–10 h) and VLDL and HDL (120 min). However, none of the blood cells tested served as acceptor for lipolysis-generated free cholesterol, whereas HDL did. In the isolated perfused rat heart, a maximum of 25% of the free cholesterol radioactivity lost from VLDL was found in the tissue. Since exchange must have contributed to this process, the transfer of free cholesterol molecules to the heart is necessarily lower. The study thus demonstrated minimal or possibly no net transport of free cholesterol from VLDL to cells and cell membranes.