DEMONSTRATION OF ANTITHROMBOPLASTIC ACTIVITY IN NORMAL AND HEMOPHILIC PLASMAS

Abstract

In plasma separated from normal human blood, collected with especial precautions, there is a substance (antithromboplastin) which, on incubation with dilute extracts of homologous brain tissue, reduces the clot accelerating action of these extracts. Antithromboplastin is exhausted during the stage preceding the inception of clotting; it has a certain degree of species specificity, is made ineffective by dilution, by heating (65[degree]C for 5 min.), by exposure to tissue juices, or by standing, especially in contact with blood cells. By reducing the amt. of available free thromboplastin released from blood or tissue cells, and thereby delaying the activation of prothrombin, antithromboplastin may play an important role in maintaining the fluidity of circulating blood and in postponing the inception of clotting of shed blood. Hemophilic plasma has an activity 5-8 times greater than that of normal plasma against certain thromboplastin solns. In standing shed hemophilic blood, more free thromboplastin and a longer time is required for the neutralization of antithromboplastin than in standing normal blood. An excess of antithromboplastin is probably the primary cause of the delay in the inception of clotting of hemophilic blood.