Dextran Sulfate Stimulated Fibrinolytic Activity In Whole Human Plasma: Dependence On The Contact Activation System And On 4 Urokinase-Related Antigen
The generation of fibrinolytic activity in whole human plasma in the presence of dextran sulfate was studied. Plasma was preincubated with N-flufenamyl-β-alanine to remove its antiplasmin and anti activator activities and then incubated with 50 μg/ml dextran sulfate (Mr - 500,000) for 30 min at 40. The initial fibrinolytic activity in 30 min, as assessed on a 125I-fibrin plate, was equivalent to approximately 9 ng/ml purified plasmin. A fraction of goat antibodies to plasminogen blocked the fibrinolytic activity of stimulated plasma, indicating that the activity was plasminogen dependent. Plasmas genetically deficient in either prekallikrein or Factor XII (Hageman Factor) showed a diminished initial rate of generation of fibrinolytic activity in response to dextran sulfate. However, after prolonged incubation (∼3 hr) of stimulated deficient plasmas with fibrin, the fibrinolytic activity approached that of stimulated normal plasma. When normal plasma was preincubated with the gamma fraction of goat antibodies made against purified urokinase, the dextran sulfate stimulated fibrinolytic activity was markedly decreased in a dose dependent manner. The data suggest that the fibrinolytic activity stimulated in whole human plasma in the presence of dextran sulfate and N-flufenamyl-β-alanine is dependent upon proteins of the contact activation system and also upon molecules immunologically related to urokinase.