title: Inhibition of platelet thromboxane A2 synthase activity by sodium 5-(3'-pyridinylmethyl)benzofuran-2-carboxylate.
abstract: This report outlines the activity of a new thromboxane synthase inhibitor sodium, 5-(3-pyridinylmethyl)-2-benzofurancarboxylate, (U-63557A). U-63557A is a potent inhibitor of the thromboxane synthase in human platelets in vitro, as well as in rhesus monkey platelets ex vivo. A single oral dose of 3.0 mg/kg U-63557A inhibits the platelet thromboxane synthase in rhesus monkeys approximately 80% for at least 12 hrs. U-63557A has been administered to monkeys twice a day, (10 mg/kg) for 14 days, without evidence of drug tachyphylaxis or rebound. U-63557A does not inhibit thrombin-stimulated PGI2 biosynthesis in human endothelial cells, the 5-lipoxygenase in human neutrophils, or the cyclo-oxygenase in a variety of test systems. In anesthetized dogs, U-63557A injected i.v. at 0.1 to 5 mg/kg prevented the blockage of stenosed coronary arteries caused platelet aggregation. Similar effects were obtained by oral administration of 1-5 mg/kg. The thromboxane synthase inhibitor was more efficacious than cyclooxygenase inhibitors and equal to PGI2 in efficacy. Under appropriate conditions the protective effects of U-63557A could be reversed by i.v. cyclooxygenase inhibitors suggesting that its efficacy depended in part on endogenous PGI2 formation. Due to its specificity, oral activity, and extended duration of action, U-63557A is a promising compound for the evaluation of the role of thromboxane synthase in a variety of pathophysiological states.
mesh_terms: D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000097:blood; D001572:Benzofurans / Q000008:administration & dosage / Q000378:metabolism*; D001792:Blood Platelets / Q000378:metabolism; D000242:Cyclic AMP / Q000097:blood; D004285:Dogs; D006801:Humans; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D013928:Thromboxane A2 / Q000096:biosynthesis*; D013929:Thromboxane B2 / Q000096:biosynthesis; D013930:Thromboxane-A Synthase / Q000037:antagonists & inhibitors*; D013931:Thromboxanes / Q000096:biosynthesis*
chemical_list: D001095:Arachidonic Acids; D001572:Benzofurans; D013931:Thromboxanes; D016718:Arachidonic Acid; D013929:Thromboxane B2; D013928:Thromboxane A2; D000242:Cyclic AMP; D010088:Oxidoreductases; D013930:Thromboxane-A Synthase; C039936:furegrelate