Abstract
Summary
1. A comparison was made of the changes in prothrombin during clotting, as indicated by the one- and 2-stage methods.
2. By the 2-stage method, progressive disappearance of prothrombin from serum was observed. Prothrombin utilization was slower in human blood than in dog blood, and was delayed greatly in canine hemophilic blood, platelet-poor human plasma, and in blood clotting in silicone-treated glassware.
3. By the one-stage method, an initial period of hypoactivity in the plasma was followed by a hyperactive phase in the serum. At the peak of hyperactivity, “prothrombin” values were about 180% of the control plasma. In slowly clotting bloods, the hyperactive phase developed less rapidly and persisted for a longer period than in normal blood. The abnormally high serum prothrombin values obtained by the one-stage test appear to be due to the evolution and persistence of the recently recognized serum factor which accelerates thrombin formation. Apparently this factor does not influence the 2-stage serum prothrombin values.
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