Platelet endoperoxide/thromboxane A2 (PGH2/TXA2 receptors in patients with myeloproliferative disorders

Abstract In patients with myeloproliferative disorders (MPD) an altered sensitivity of platelets to antiaggregatory prostaglandins and to the endoperoxide analogue U 46619 has been found. In this study we examined U 46619-induced platelet aggregation and binding of the endoperoxide/thromboxane A 2 (TXA 2 ) receptor antagonist SQ 29548 in 11 patients with MPD and 11 healthy controls. Although platelet responsiveness to U 46619 was significantly enhanced (p 2 receptor were not altered (Bmax 0.67 ± 0.20 vs. 0.58 ± 0.14 pmol109 platelets, K d 0.41 ± 0.11 vs. 0.55 ± 0.09 mM). These data exclude the possibility that changes in the presentation of endoperoxide/TXA 2 receptors are responsible for the enhanced platelet sensitivity to endoperoxides found in MPD.