EFFECTS OF PHOSPHATIDYLSERINE ON THE OXIDATION OF LOW-DENSITY-LIPOPROTEIN

1. LDL was incubated in the presence of 1 mu M CuSO4 for 18 hr at 37 degrees C. The content of lipoperoxides was found to be approx. 40 nmol MDA equivalents/mg LDL protein. The addition of 50 mu M phosphatidylserine (PS) reduced the content of lipoperoxides to 15% of control values. 2. The electrophoretic mobility observed for LDL oxidized in the presence of PS approximated the mobility observed for native LDL. 3. The formation of conjugated dienes was strongly inhibited when LDL was oxidized in the presence of PS. 4. The addition of 50 mu M phosphatidylcholine, phosphatidylglycerol and cardiolipin did not alter the extent of LDL oxidation. 5. PS did not inhibit the oxidation of LDL mediated by J774 macrophages in the presence of Ham's F-10 culture medium. Under these conditions, PS was found to be an excellent substrate for oxidation.