The Influence of Human Blood Cells on the Solubility of Clot in Urea Solution and Clot Lysis

Summary

A proteolytic factor digesting fibrin in concentrate urea solution was demonstrated in granulocytes, erythrocytes and blood platelets.

The proteolytic factor is not dialysable, is inactivated at temp. 80°, and produces low molecular weight peptides when digesting clot. Its action on fibrin is dependent on the presence of urea, but urea does not activate it permanently. In granulocytes the factor is present in an active form, and in red blood cells it is located in the stromata, its activity being suppressed by an inhibitor adsorbed on the surface of the cells. Red blood cells exhibit proteolytic activity only after several washings with physiological saline solution.

Increased solubility of full blood clots in urea can be brought about by addition of an excess of active proteolytic factor (concentrated granulocyte or washed red blood cell suspensions) to the clot, or by prior washing of the clot with physiological saline (to remove the inhibitor). Noncellular clots (fibrin, plasma clots) may be dissolved in urea only after addition of granulocytes, platelets or activated red cells.

The possible role of this proteolytic activity in the in vivo liquefaction of blood clots is discussed.

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