NATIVE LIPOPROTEINS INHIBIT PLATELET ACTIVATION-INDUCED BY OXIDIZED LIPOPROTEINS

Copper-catalyzed oxidation of low-density lipoproteins (LDL) (0.8 g pr otein/l LDL, 20 mu mol/l CuSO4, 37 degrees C) resulted in the formatio n of thiobarbituric reactive substances that was substantially complet e at 24 hrs whereas their formation from high-density lipoproteins (HD L) plateaued at only 25% of that amount after 8 hrs. The oxidized lipo proteins induced aggregation and increases in [Ca2+]i in washed platel ets, but not in platelet-rich plasma, and these activating effects wer e not inhibited by aspirin or EGTA but were inhibited by both of the n ative lipoproteins. These results show that oxidized HDL, like oxidize d LDL, have platelet activating ability and suggest that the native li poproteins may play a crucial role in preventing the oxidized lipoprot ein-mediated platelet activation. (C) 1996 Academic Press, inc.