Exchange of phospholipids between unilamellar vesicles of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine and plasma very low density lipoproteins

Purified phosphatidylcholine exchange protein from bovine liver was used to exchange [¹⁴C]dipalmitoyl phosphatidylcholine from sonicated vesicles to human plasma very low density lipoproteins (VLDL). The exchange of [¹⁴C]-dipalmitoyl phosphatidylcholine for VLDL phospholipids was temperature dependent and linear with respect to time and amount of exchange protein. In the absence of the exchange protein, less than 10% of the [¹⁴C]dipalmitoyl phosphatidylcholine was transferred. At an initial weight ratio of [¹⁴C]-dipalmitoyl phosphatidylcholine vesicles to VLDL phospholipid (1.2 mg) of 2.2, the exchange protein (14μg) replaced 55% of the VLDL phospholipids with [¹⁴C]dipalmitoyl phosphatidylcholine in 15 min; VLDL protein and cholesterol content were unaltered. From these studies we conclude that the exchange protein is a useful method to alter the phospholipid composition of VLDL under conditions such that there is minimal perturbation of the lipoprotein.