The endothelium of blood vessels is of great importance in maintaining blood fluidity and modulating thrombogenesis. Endothelin (ET) participates in thrombogenesis and its role in the pathogenesis of heart diseases such as acute myocardinal infarction has been proved, but little is known about the effect of ET on thrombolysis. Using a model of thrombosis in rat abdominal aorta induced by direct current-ferric trichloride, we found that the plasma ET level was 3.7 times the baseline after lysing the thrombus with urokinase (250,000 U/kg) while 5 micrograms/kg of exogenous ET prolonged the time of thrombolysis to 115% of baseline control. Plasma ET level was six times the baseline level. Incubation of a rat aortic strip in vitro with taurine (20 mmol/L) had no effect on baseline ET release, but taurine prohibited the stimulation of thrombin and A23187 of ET release in a dose-dependent way. Plasma ET decreased between 17 and 40% after injection of taurine, which also decreased by 45% the time of lysis of thrombus. From the above data it might be concluded that ET inhibits thrombolysis and that the abnormally increasing plasma ET can be attenuated by taurine, which is beneficial to thrombolysis.