Release of B19 peptides and F (g) DP from fibrin (ogen) was studied after the activation of Glu-plasminogen (Glu-plg) by urokinase (UK) in the plasma or clot and fibrinogen or fibrin. B,3 peptides or FDP were released faster from the clot than the plasma. In a purified system, FDP was released faster than FgDP after the activation of Glu-plg by UK in the presence of fibrin or fibrinogen. Release of Bj3 15-42 from purified fibrin was slower than the release of Bj3 1-42 from fibrinogen when

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... g was activated by UK. The presence of a2 antiplasmin (a2AP) slowed the release of Bj3 1-42 from fibrinogen, thus resulted in faster release of Bj3 15-42 in comparison to Bj3 1-42. These results indicated that Glu-pig was activated better by UK in the presence of fibrin than fibrinogen, but the release of Bj3 peptides from purified fibrin and fibrinogen depended upon the presence of a2AP. Since fibrin prevented inactivation of plasmin by a2AP, the presence of a2AP inactivated plasmin in the fluid phase.