WS-7338, NEW ENDOTHELIN RECEPTOR ANTAGONISTS ISOLATED FROM Streptomyces sp. No. 7338

WS-7338, produced by Streptomyces sp. No. 7338, was found to be a competitive and specific antagonist against ET-1 receptors in in vitro studies and WS-7338 B is also active in vivo. Furthermore, WS-7338 B was a specific antagonist for vascular ET-1 receptors (ETA receptors) and significantly prevented the accumulation of intracellular inositol 1, 4, 5-triphosphate (IP3) in endothelin treated rat aorta tissues.