Effects of ω -aminoacids and clot formation on the activation by urokinase of various plasminogen preparations

Abstract

Effects of clot formation and ω -aminoacids on the activation rates of various forms of plasminogen by urokinase (UK) were studied. The activation rates of Glu-plasminogen (including Plg-I and II) increased in the presence of fibrin, while little difference was observed in the activation rate of Lys-plasminogen in the presence and absence of fibrin. The activation rate of acid treated plasminogen (A-plg) was smaller in the presence of fibrin than in its absence. Increase in the concentration of ω -aminoacids first resulted in increase in the activation rates of Glu-forms of plasminogen of which the peak values were obtained at 1 mM for tranexamic acid, 10 mM for 6-aminohexanoic acid (6AHA), and 100 – 1,000 mM for L-lysine. Further increase in the concentration of tranexamic acid, and 6AHA resulted in decrease in the activation rates. The activation rate of Lys-plasminogen slightly increased with increase in the concentration of tranexamic acid. The activation rate of A-plg decreased with increase in the concentration of tranexamic acid, and 6AHA. In the clot, the activation rate of Glu-plasminogen first slightly decreased and then increased with increase in the concentration of ω-aminoacids. Activation was almost totally inhibited at 10 mM of tranexamic acid. Fibrinolysis showed some inhibition at 0.01 mM of tranexamic acid at which concentration slight decrease in the activation rate was observed, then almost total inhibition was observed at 1 mM which was a peak value in the activation rate. In conclusion, interaction of ω-aminoacids or fibrin with lysine binding sites of plasminogen may result in different effects on the activation rate by UK, depending upon different forms of plasminogen. Possibly different lysine binding sites may have different roles in the influence on the activation rate of plasminogen.