Human chorion cells have been broken open and separated into “nuclear”, “mitochondrial”, “microsomal” and soluble fractions by differential centrifugation in the cold. Minute quantities of the homogenate and individual cell fractions were immediately tested for their fibrinolytic activity on fibrin plates with and without plasminogen, and also in the presence of streptokinase, ε-aminocaproic acid or Triton X-100.With the technique employed, no direct fibrinolysis was produced by the homogenate or cell fractions. In the presence of streptokinase the homogenate and cell fractions led to marked fibrinolysis indicating the presence of cellular proactivator activity. Comparison of the intracellular fractions indicated that the greatest proactivator activity was associated with the “microsomal fraction”. The streptokinase-induced proactivator activity was partly inhibited by certain concentrations of ε-aminocaproic acid.
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