Platelet-modified lipoprotein induced by thrombin: effect of whole blood and plasma.

The effect of thrombin, the platelet-activating agent, on lipids and lipoprotein patterns in humans was studied in whole blood, in platelet-rich plasma (PRP) and in washed platelet/lipoprotein systems. Upon incubation of whole blood at 37 C for 24 h and then centrifugation of the cells, the content of plasma cholesterol and triglyceride decreased. In the presence of thrombin (10 u/ml), plasma high-density lipoprotein (HDL) levels also markedly decreased. In PRP, plasma lipids and lipoproteins were reduced to a lesser extent than in platelet-poor plasma (PPP). In the presence of thrombin, plasma HDL was decreased in PRP, but not in PPP. The electrophoretic mobility of low-density lipoprotein (LDL) was increased following incubation of whole blood, PRP or PPP, but decreased in the presence of thrombin. When washed platelets were incubated with LDL or HDL for 24 h at 37 C, there was a significant increment in the lipid and protein content of the lipoprotein medium, resulting from platelet-released particles; this phenomenon was increased in the presence of thrombin and more so with LDL. LDL--but not HDL--electrophoretic mobility was increased following incubation with washed platelets, but thrombin caused a reduction in lipoprotein electrophoretic mobility. This study demonstrates that platelets affect lipid and lipoprotein patterns and this is influenced by thrombin treatment. Platelets release lipid-protein particles, which then interact with and modify the lipoprotein.