Plasmin, Plasmin Inhibitors and Degradation Products of Fibrinogen in Human Serum during and after Intravenous Infusion of Streptokinase

Abstract

The variation of plasminogen, plasmin, plasmin inhibitors, fibrinogen and its split products were estimated in sera obtained from three patients before, during and after intravenous infusion (24 hours) of streptokinase.

Practically all plasminogen was activated to plasmin within the first four hours of the infusion. The plasmin was recovered mainly as a complex with the ‘immediate inhibitor’ i.e. α₂-macroglobulin. This complex was almost completely eliminated within 24 hours, during which time the α₂-macroglobulin concentration decreased by about 50 per cent. The α₂-macroglobulin did not quite recover its original concentration during the observation period (up to 16 days). The plasminogen recovered its initial concentration within 48 hours after the end of the infusion. No complex formation could be demonstrated between plasmin and the ‘slow inhibitor’ i.e. α₁-antitrypsin. The concentration of α₁-antitrypsin increased markedly after the infusion of streptokinase.

The ‘thrombin inhibiting capacity’ of the macroglobulin fractions after gel filtration varied mainly with the α₂-macroglobulin concentration, while the inhibiting capacity of the fractions containing albumin was almost unchanged during the infusion of streptokinase.

In spite an excess of α₂-macroglobulin in plasma, fibrinogen was degraded to products of varying molecular size. The concentration of the degradation products was highest 4 hours after the beginning of the infusion. Only trace amounts were demonstrable 24 hours after the end of the infusion.

Key Words:

• Fibrinogen
• fibrinolysin
• fibrinolysis
• plasminogen
• streptokinase
• trypsin inhibitors