The fibrinolytic system and haemostasis.

The fibrinolytic enzyme system appears to be a parallel development with the plasma coagulation pathways involved in haemostasis. Both systems have common activation mechanisms, inhibitors and the enzymes involved have considerable homology. In addition, blood cells show capabilities for involvement in each of these systems. There is disagreement over the possible contribution of the fibrinolytic mechanism to normal fibrinogen catabolism either by the lysis of continually forming fibrin, or by degradation of circulating fibrinogen. The occurrence of systemic fibrinolysis is associated with haemorrhagic tendency which may be due to a number of factors including degradation of coagulation factors, the anticoagulant effect of F.D.P. and the lysis of alpha-chain crosslinking sites. A clinical study of patients treated with streptokinase indicates that a fall in plasma fibrinogen levels and increase in serum F.D.P. levels are correlated with the haemostatic defect.