Abstract: AIM: To observe the in vitro effect of papain on blood coagulation function, and to explore the possible mechanism. METHODS: Human platelet poor plasma (PPP) and platelet rich plasma(PRP) were mixed with different dose of papain which were assigned into three groups (group 0 U/L, group 10 U/L and group 20 U/L). PPP and PRP were measured for prothrombin time(PT) and actvated partial thromboplastin time (APTT) with blood coagulation analyzer, the PPP was also measured for Ca²⁺ and activity of coagulable factor V, VII, VIII, IX, X and XI(FV:C、FVII:C、FVIII:C、FIX:C、FX:C and FXI:C) with blood-gas analyzer and blood coagulation analyzer, respectively. Fresh blood from volunteers was mixed with the three dose of papain, the clotting time(CT) was detected with silicified tube method. The PPP with 0, 20, 40,60 and 80 U/L of papain also was measured for PT and APTT.RESULTS: At group 10 U/L papain and group 20 U/L papain, PT and APTT of PPP and PRP as well as CT of whole blood was significantly higher, but FV:C and FVIII:C activity was remarkably lower than that at group physiological saline solution and group 10U/L papain, respectively. There was no statistical difference for PT and APTT between PPP and PRP at the three groups, for Ca²⁺ concentration and other four coagulable factors activity between the three groups one another. Either PT or APTT level at group 0,20, 40,60and 80U/L of papain showed positive correlation with papain dose. CONCLUSION: Papain has dose-dependent inhibitory effect on blood coagulation mainly through inhibition of coagulable facor V and VIII activity. Papain has the efficacy of anticoagulation

Key words: Papain, Blood coagulation function, Coagulable factor V, Coagulable VIII, Anticoagulation