ON THE CONSTITUTION OF PROTHROMBIN

Abstract

Evidence is presented that prothrombin is composed of 2 components (A and B) which are united through Ca. Component A is relatively labile and diminishes in stored oxalated or citrated plasma, presumably due to destruction by oxidation. Component B disappears from the blood of animals poisoned with dicumarol. It is adsorbed from oxalated plasma. In undecalcified plasma, no diminution of component A occurs, nor is component B adsorbed by A1(OH)3. This suggests that the components are combined with Ca and are resistant to destruction and adsorption. Ca is a part of the prothrombin molecule; with increasing additions of Na citrate to blood or plasma, the coagulation time in the presence of excess thromboplastin is progressively delayed. More Na citrate is needed to depress the coagulation of rabbit blood than human blood, which indicates that the prothrombin content of rabbit blood is considerably higher. The concept that prothrombin is a complex of 2 components and Ca aids in formulating conditions for the quantitative detn. of prothrombin, validates on theoretical grounds the use of stored plasma transfusions for treating hemorrhage due to dicumarol, and makes possible a more accurate classification of the clinical conditions of hypoprothrombinemia.