Warfarin Induced Fibrinolysis: The Effect Of Recovery With And Without Vitamin K
We have previously shown that fibrinolysis in the rat is enhanced by levels of warfarin administration sufficient to produce moderate anticoagulation. This effect is mediated largely by an increase in plasma plasminogen activator. Plasminogen levels are decreased and fibrin(ogen) degradation products raised confirming the presence of a systemic hyperfibrinolytic state. In order to investigate this phenomenon further we have measured fibrinolytic components in rats recovering from warfarin administration. Groups of male Hooded rats received 14 yg warfarin/100 g body weight /day by mouth for one to two weeks. The animals were then allowed to recover without further treatment or following a single 50 μg dose of vitamin K1. Euglobulin lysis time, one stage prothrombin time, plasma plasminogen activator (fibrin plate method), plasma plasminogen (caseinolytic method), plasma fibrinogen (clot weight method) and plasma fibrinolytic inhibitors were measured at intervals after the end of the warfarin treatment. In animals recovering without vitamin K prothrombin time returned to normal within one week. However fibrinolysis remained elevated with plasma plasminogen activator concentrations of more than twice the control value. Plasma inhibitor levels were depressed and fibrinogen levels elevated. After two weeks all fibrinolytic components had returned to normal. Following vitamin Kj administration a different pattern emerged; prothrombin time returned to normal within 24 hours but fibrinolysis was diminished. The latter effect was due to a marked increase in plasma fibrinogen and moderate fall in plasma plasminogen activator both of which contributed to a prolonged euglobulin lysis time. These results indicate that fibrinolysis and coagulation in the rat are not linked in a 'dynamic equilibrium' like that proposed for man. The enhanced fibrinolysis rather than being a result of the fall in vitamin K dependant clotting factors may be due to the direct action of warfarin. The 'fibrinolytic shutdown' following vitamin K remains unexplained .