Effects of α₂-Plasmin Inhibitor on Fibrin Clot Lysis. Its Comparison with α₂-Macroglobulin

Summary

The major plasmin inhibitors namely α₂-plasmin inhibitor and α₂-macroglobulin were compared for their effects on lysis of fibrin clot.

Plasmin fibrinolytic activity was immediately inhibited by α₂-plasmin inhibitor, whereas α₂-macroglobulin inhibited plasmin progressively. Urokinase(plasminogen activator)-induced clot lysis was inhibited efficiently by α₂-plasmin inhibitor present in the clot. Inhibition of urokinase-induced clot lysis by α₂-macroglobulin was weak and the molar concentration necessary for α₂-macroglobulin to achieve the same degree of inhibition as that achieved with α₂-plasmin inhibitor was about 10 times higher than that of α₂-plasmin inhibitor.

Binding of Lys-plasminogen to fibrin was inhibited by α₂-plasmin inhibitor but not by α₂-macroglobulin. Molar concentrations of α₂-plasmin inhibitor which were effective in inhibiting the binding were 30 times less than that of 6-aminohexanoic acid. α₂-Plasmin inhibitor was found to interact with Lys-plasminogen to form a weakly-bound complex which is dissociable in the presence of 6-aminohexanoic acid, suggesting that inhibition of binding of Lys-plasminogen to fibrin by α₂-plasmin inhibitor may be due to interaction of α₂-plasmin inhibitor with a specific site of the plasminogen molecule and that the site may be 6-aminohexanoic acid-binding site.

It is suggested that α₂-plasmin inhibitor is more reactive and efficient inhibitor of fibrinolysis than α₂-macroglobulin.

• References

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