FIBRIN, A FACTOR INFLUENCING THE CONSUMPTION OF PROTHROMBIN IN COAGULATION

Abstract

The prothrombin consumption time which measures the amt. of prothrombin remaining in serum after coagulation serves as a means to determine the free or available thrombo-plastin of the blood. For active thromboplastin to become available platelets must disintegrate to furnish the enzyme activator for thromboplastinogen and thrombin must form to cause lysis of platelets. Due to the active adsorption of thrombin by fibrin, the thrombinogenic chain reaction is held in check and very little prothrombin is consumed. Separation of serum from intimate contact with fibrin either spontaneously by clot retraction or mechanically by centrifuging, initiates the auto-catalytic process and prothrombin diminishes rapidly. To determine the true content of prothrombin in clotted blood, Na citrate was added to the unretracted clot before centrifuging, thereby preventing any conversion of prothrombin during centrifuging. On the basis of these observations, the prothrombin consumption test is standardized. Fixed volumes of blood are allowed to clot, and after specific periods a sample is centrifuged and the prothrombin remaining in the serum determined at 15 min. intervals during one hour. Studies of the prothrombin consumption in normal, hemophilic and thrombo-cytopenic blood are reported. In the latter 2 conditions very little prothrombin is converted. The significance of the anti-thrombic activity of fibrin in venous thrombosis is discussed and the danger of clot retraction by expressing a. thrombin-rich serum is pointed out.