The fibrinolytic system is antagonist to the coagulation system, dissolving fibrin clots by the specific and powerful protease plasmin.
The importance of the fibrinolytic system in keeping the vascular tree free of clots is suggested by the site of synthesis of 2 regulatory components, t-PA (tissue plasminogen activator) and PAI-1 (plasminogen activator inhibitor)--in endothelial cells. Plasmin is synthesized as a proenzyme (plasminogen) in the liver.
