Abstract: Objective To observe the dynamic changes of urokinase-type plasminogen activator(uPA) and its receptor(uPAR) in rats after pulmonary thromboembolism(PTE) and their relationship to spontaneous thrombolysis rate.Methods PTE was induced in Male Sprague Dawley(SD) rats through injecting heated(125)iodine-labeled fibrinogen autologous thromboembolic into external jugular veins.Thirty-five rats were randomly assigned into following groups(each 7): 1) Healthy control group;2) PTE group including PTE 4 h group,PTE 24 h subgroup,PTE 3 d subgroup,PTE 5 d subgroup.The rats were separately sacrificed at 4 h,24 h,3 d,5 d after the PTE model was successfully made.Plasma samples were extrated and reserved for analysis of urokinase-type plasminogen activator(uPA) and its receptor(uPAR),so were hearts,lungs and whole blood for spontaneous thrombolysis rate.Results 1) Plasma concentrations of uPA and uPAR elevated after PTE(24 h P<0.05;3 d P<0.01;PTE 5 d uPA P<0.05,uPAR P<0.01)and reached a peak valuein PTE 3 d group,then began to decrease in PTE 5 d subgroup.Plasma concentration of uPA was positively correlated with spontaneous thrombolysis rate after PTE in 4 h,24 h,3 d subgroups(4 h r=0.758,P<0.05;24 h r=0.764,P<0.05;3 d r=0.778,P<0.05),so was plasma uPAR(4 h r=0.701,P<0.05;24 h r=0.764,P<0.05;3 d r=0.777,(P<)(0.05)).Histopathological results of the lung: Secondary thrombosis and infiltration of leukocyte in thrombus and vascular wall was observed in PTE 4 h subgroup.The injected clot was obviously dissolved in PTE 3 d and 5 d subgroup replaced by secondary thrombus.Conclusion 1) Plasma levels of endogenous uPA and uPAR are increased at different time points after PTE which promote endogenous fibrinolysis.

Key words: pulmonary thromboembolism, uPA, uPAR, fibrinolysis