Modulation of TXA 2 generation of platelets by human lipoproteins

Abstract

The lipoprotein (LP) fractions VLDL, LDL, HDL 2 and HDL 3 were prepared by ultracentrifugation of plasma from healthy volunteers and from patients with coronary heart disease (CHD). We investigated the capacity of platelets from healthy volunteers and patients with atherosclerosis to generate thromboxane A 2 (TXA 2) during spontaneous clotting of whole blood under the influence of the lipoprotein fractions. In our experiments the serum concentration of TXB 2, reflecting the capacity of platelets to generate TXA 2 during clotting, depends on several factors: the type of LP fraction used, the blood used for generation of TXA 2, and for the same LP fraction whether it was taken from plasma of healthy volunteers or patients with CHD, VLDL prepared from plasma of healthy volunteers inhibited but VLDL prepared from plasma of patients with CHD enhanced the TXA 2 formation of platelets from healthy volunteers (p < 0.05, resp.). LDL from CHD patients inhibited the TXA 2 formation of platelets from atherosclerotic patients (p < 0.01). The HDL subfractions HDL 2 and HDL 3 from healthy volunteers inhibated TXA 2 formation by platelets from healthy volunteers as well as those from atherosclerotic patients (p < 0.05; p < 0.01, respectively). HDL 2 from patients with CHD inhibited only the TXA 2 formation of platelets from healthy volunteers (p < 0.01), whereas HDL 3 from CHD patients inhibited only the TXA 2 formation of platelets from atherosclerotic patients (p < 0.01).