WS009 A and B, new endothelin receptor antagonists isolated from Streptomyces sp. No. 89009. II. Biological characterization and pharmacological characterization of WS009 A and B

WS009 A and B, produced by Streptomyces sp. No. 89009, were found to be competitive and specific antagonists against endothelin (ET)-1 receptors in in vitro studies and also active in in vivo studies. Furthermore, WS009 A and B were specific antagonists for vascular ET-1 receptors (ET A receptors) and significantly prevented the accumulation of intracellular inositol 1,4,5-triphosphate (IP 3 ) in endothelin treated rat aorta tissues