Studies of the “Thrombin” Effect of Fresh Serum. *

Abstract

A factor capable of producing prothrombin conversion has been described in a previous report.¹ This factor can be easily demonstrated after thromboplastin is added to serum which contains no thrombin and only traces of prothrombin. The resultant mixture of serum and thromboplastin causes rapid coagulation of a 0.01 M oxalated plasma. † Suitable control studies revealed that this factor (designated “prothrombin-converting factor”), is not thrombin, but a substance which requires prothrombin to mediate a coagulation effect on fibrinogen. Furthermore, the coagulation of 0.01 M oxalated plasma by the serum-thromboplastin mixture could not be explained as a separate action of either component.