High density lipoprotein 3 (HDL
3=1.12<
d<1.21) was modified with dilinoleoylphosphatidylcholine, and the effects of these modified HDL
3 on the removal of [
3H]cholesterol from rat peritoneal macrophages were studied. On incubation of HDL
3 with polyenephosphatidylcholine (PPC) vesicles, phospholipid-rich high density lipoproteins (1.18<
d<1.24) were formed. The apolipoprotein AI (apo AI) and AII (apo AII) contents of these modified HDL
3 were about 3 to 40% of those of native HDL
3. Removal of [
3H]cholesterol from macrophages was investigated using rat peritoneal macrophages prelabeled with [
3H]cholesterol emulsion or with [
3H]cholesterol oleate-labeled acetylated low density lipoproteins (1.019<
d<1.063). The modified HDL
3s facilitated the removal of [
3H]cholesterol from macrophages. The extent of removal of [
3H]cholesterol from macrophages was higher with modified HDL
3 than with native HDL
3, and among modified HDL
3 subfractions, fractions IV and V, whose ratio of apo AI to phospholipid (AI/PL) were 0.44 and 0.58, respectively, were more efficient [
3H]cholesterol acceptors than native HDL
3 (AI/PL=1.46). These results indicate that the effectiveness of HDL
3 in removing [
3H]cholesterol from macrophages was enhanced by modification with PPC.
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