Abstract
High density lipoproteins are known to have a function to remove cholesterol from the peripheral tissues. To study the mechanism of cholesterol removal by HDL, and to multiply the function of HDL, modified HDL was prepared with polyenphosphatidylcholine vesicles (soya bean lecithin=dilinoleoyl phosphatidylchone>60%, deoxycholic acid (250mg/500mg PPC) and their functions were studied. PPC vesicle itself increased the release of [3H] cholesterol from [3H] cholesterolladen peritoneal macrophages of rats and was much more efficient than dipalmitoyl phosphatidylcholine vesicles. Apolipoprotein AT, CI and CIII alone did not enhance the release of [3H] cholesterol, but in the presence of PPC vesicles or DPPC vesicles, these Apolipoproteins augumented the releases of [3H] cholesterol from macrophages. Incubation of PPC vesicle with HDL formed new complexes. These complexes eluted at density from 1.14 to 1.28 in zonal ultracentrifugation and were poor in apoprotein AI and AII (2.5% or 25% of that in native HDL) and rich in phospholipid. The addition of modified HDL to macrophages which were preincubated with [3H] cholesterol or [3H] cholesterol oleate-labeled acetylated low density lipoprotein, increased the release of [3H] cholesterol from the cells. Their releasing activities were greater than native HDL, when the releasing activity was expressed as a function per protein concentration of HDL or modified HDL. These results suggest that removal of [3H] cholesterol from the macrophages was multiplied by modifying HDL with PPC vesicles.
