sq-29548 and Myeloproliferative-Disorders

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 A2 (TXA2) receptor antagonist SQ 29548 in 11 patients with MPD and 11 healthy controls. Although platelet responsiveness to U 46619 was significantly enhanced (p less than 0.05) in MPD, binding affinity and binding capacity of the corresponding endoperoxide/TXA2 receptor were not altered (Bmax 0.67 +/- 0.20 vs. 0.58 +/- 0.14 pmol/10(9) platelets, Kd 0.41 +/- 0.11 vs. 0.55 +/- 0.09 nM). These data exclude the possibility that changes in the presentation of endoperoxide/TXA2 receptors are responsible for the enhanced platelet sensitivity to endoperoxides found in MPD.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adult; Aged; Blood Platelets; Bridged Bicyclo Compounds, Heterocyclic; Fatty Acids, Unsaturated; Female; Humans; Hydrazines; In Vitro Techniques; Kinetics; Male; Middle Aged; Myeloproliferative Disorders; Platelet Aggregation; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic; Receptors, Prostaglandin; Receptors, Thromboxane