Summary
The roles of platelet aggregation and coagulo-fibrinolytic systems in thrombogenesis
of lactic acid-induced pulmonary thrombosis in rat were studied using an anti-coagulant,
platelet aggregation inhibitor, fibrinolytic or anti-fibrinolytic agents.
In normal rat, heparin (2.5 mg/kg), acetylsalicylic acid (30 mg/kg) and tranexamic
acid (100 mg/kg) suppressed specifically coagulation, platelet aggregation induced
by collagen or thrombin and fibrinolysis respectively. Urokinase (10,000 units/kg)
activated powerfully fibrinolytic system in addition to suppressing slightly platelet
aggregation.
The pretreatment with heparin, acetylsalicylic acid or urokinase markedly prevented
the formation of thrombus initiated by the infusion of lactic acid at the doses used.
Additive effect was also obtained by combined administration of these agents. On the
other hand, it was interesting to note that tranexamic acid (100 mg/kg) did not affect
the thrombus formation at all despite a potent anti-fibrinolytic effect of this agent.
These results indicate that both platelet aggregation and enhancement of coagulation
activity are important factors responsible for the formation of thrombi in DIC, while
the fibrinolytic activity in blood seems not to be involved in it. On the basis of
the findings, mechanism for triggering activation of coagulation and platelet aggregation
is also discussed here.
