Modification of the Fibrin Agar Plate for Measurements of the Components of the Fibrinolytic System

Summary

Human fibrinogen solutions were heat coagulated in 1 % agar solution at 85° C. The salt and pH of the medium was varied and the conditions found in which plasminogen and plasminogen activator originally present in the fibrinogen were completely heat inactivated. The resultant fibrin agar plates only showed lysis when plasminogen and plasminogen activators were re-introduced simultaneously. A pH 8.5 sequestrene saline buffer proved to be the most sensitive medium for both streptokinase and urokinase activation of human plasminogen. Plasminogen estimations on these Type I plates gave the following results :

1. Alteration in some M. R. C. standard plasminogen preparations resulting in a selective loss of response to SK activation in specimens stored in solution at —30° C.

2. Irreversible plasminogen inactivation by mixing euglobulin or purified plasminogen with high SK concentrations.

3. Normal numerical mean plasma and serum plasminogen levels of 12 casein u/ml confirming earlier results of a lysis time method. The factor leading to underestimation of plasma plasminogen by a caseinolytic estimation were investigated and discussed.

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