Technical Remarks on the Microscopical Demonstration of Tissue Plasminogen Activator

Summary

The authors examine some variables capable of influencing the results obtained with the fibrin slide technique for microscopical demonstration of fibrinolytic activators in tissues (Todd’s method).

The speed of freezing of the tissue specimen proved to be especially important. Slow freezing of the specimen should be avoided since it results in sections of poor quality and may alter the distribution of fibrinolytic activity. The optimal thickness of the sections lies between 6 and 8 (jim. The concentration of fibrinogen used as substrate may vary between 0.7 and 2.0% and the thickness of the fibrin film between 0.07 and 0.21 mm. Increasing the temperature of incubation from +4° C to +37° C enhanced fibrinolysis, but had no effect on the distribution of fibrinolytic activity in the sections. Storage of the sections at —20° C and at +4° C for 6 days had no apparent effect on their fibrinolytic activity. Storage at 28° C resulted in a considerable loss of the fibrinolytic activity of the sections. The error of a method to assess the strength of fibrinolytic activity of the section is determined.

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