DIRECT ANTAGONISM OF THE TXA2 BLOOD PLATELET RECEPTOR

我们先前报道了一个化合物的合成和药理活性。 一系列直接抑制人血小板的新化合物 血栓素A2/前列腺素H2(TXA2/PGH2)受体。结果发现， 这些试剂，特别是13-氮杂前列烷酸(13-APA)2， 拮抗TXA2/PGH2诱导的血小板活化 对其他生理激动剂诱导的血小板活化的影响。在……里面 在目前的提议中，已经设计了现在雇用这些代理人的研究 作为研究其潜在机制的选择性药理学工具 与TXA2/PGH2诱导的血小板活化有关。具体来说， 建议使用(~3H)13-APA进行结合研究的实验 完整的血小板和血小板膜制剂。这些研究应该 提供第一个直接证据证明存在和定位 血小板TXA2/PGH2受体。为了识别和表征 这个推测的受体的蛋白质组成，一种放射性标记的烷基化 将使用13-APA的衍生物。此外，实验还包括 建议更清楚地建立TXA2和PGH2的相对能力 导致血小板活化。通过使用竞争性受体 本方案中建立的结合实验和选择性TXA2合成酶 抑制剂，应该可以确定PGH2是否是 它本身能够与血小板受体相互作用。最后，我们会 探讨直接TXA2/PGH2受体单独拮抗或 联合前列环素可作为一种有效的治疗手段 降低体内的血小板反应性。除了上述研究外，还有一项 将进行合成计划以开发新的试剂，这应该是 对进一步表征TXA2/PGH2的参与具有重要价值 在血小板活化方面。这项计划将涉及合成新的 研究与之相互作用的结构要求的化合物 TXA2/PGH2受体及其修饰产物的合成 13-氮杂前列腺素(用于亲和层析)纯化受体 地点。因此，这一提议的广度从分子延伸到 血栓素A2与其受体的相互作用及其在血管紧张素转换酶中的应用 TXA2拮抗剂对体内血小板活化的抑制作用。这 方法应该为未来的发展提供更合理的基础 在治疗血栓栓塞性疾病中有用的药理物质。

We previously reported the synthesis and pharmacological activity of a series of new compounds which directly inhibit the human blood platelet thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptor. It was found that these agents, in particular 13-azaprostanoic acid (13-APA)2, specifically antagonize platelet activation induced by TXA2/PGH2, with virtually no effects on platelet activation induced by other physiological agonists. In the present proposal, studies have been designed to now employ these agents as selective pharmacological tools to investigate the underlying mechanism associated with TXA2/PGH2-induced platelet activation. Specifically, experiments are proposed to perform binding studies using (3H) 13-APA in intact platelets and platelet membrane preparations. These studies should provide the first direct evidence for the existence and location of a platelet TXA2/PGH2 receptor. In order to identify and characterize the protein composition of this presumed receptor, a radiolabeled alkylating derivative of 13-APA will be employed. In addition, experiments are proposed to more clearly establish the relative ability of TXA2 and PGH2 to cause platelet activation. Through the use of a competitive receptor binding assay developed in this proposal and selective TXA2 synthetase inhibitors, it should be possible to establish whether or not PGH2 is itself capable of interacting with a platelet receptor. Finally, we will explore the possibility that direct TXA2/PGH2 receptor antagonism alone or in combination with prostacyclin may serve as an effective means of reducing platelet reactivity in vivo. In addition to the above studies a synthetic program will be undertaken to develop new agents which should be of substantial value in further characterizing the involvement of TXA2/PGH2 in platelet activation. This program will involve the synthesis of new compounds to investigate the structural requirements for interaction with the TXA2/PGH2 receptor, as well as the synthesis of a modified 13-azaprostanoid (for affinity chromatography) to purify the receptor site. The breadth of this proposal therefore extends from the molecular interaction of TXA2 with its receptor to the application of TXA2-antagonists to the inhibition of platelet activation in vivo. This approach should provide a more rational basis for the future development of pharmacological agents useful in the treatment of thromboembolic disorders.