Fibrinolysis and Coagulation. I.: Effect of Calcium on Lysis of Euglobulin Clots

The effect of various concentrations of calcium on lysis of euglobulin clots was studied. If clot lysis times exceeded 200 minutes, 0.5 mM CaCl2 or less inhibited the process, whereas higher concentrations accelerated clot lysis. If clot lysis times were short, high calcium concentrations inhibited clot lysis. This happened if enhanced activity was obtained by removal of inhibitors or if it was obtained by a higher activator concentration. These effects of calcium were related to its procoagulant effect and disappeared on adsorbtion with BaSO4. Euglobulin from patients with severe coagulopathies revealed a reduced accelerating effect of calcium. The calcium effect on clot structure was probably of minor importance.