Differences in the Binding to Fibrin of Urokinase and Tissue Plasminogen Activator

Abstract

It has been reported by many investigators that platelets adhere to collagen fibers (9) and by us that platelets adhere to injured endothelial cells in vivo in small mesenteric arterioles in guinea pigs (2). This study shows platelets aggregating to form thrombi on the amorphous cytoplasm of endothelium where the ATP-ase activity has been located and where some unrecognizable part of the basement membrane may exist. It is postulated that injury to the endothelial cell exposes these ATP-ases which release the adenosine diphosphate observed in the blood in the damaged vessel, to initiate thrombi formation.