Prothrombin Conversion Factors in Blood Coagulation

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Abstract
Instead of there being only the one conversion factor, thromboplastin, of the classical clotting theory, evidence continues to accumulate that other substances are necessary for prothrombin conversion to thrombin. One such factor, the labile factor, is characterized by its disappearance from plasma or serum at rates varying with the temp. Its concn. did not seem to be seriously altered by dicumarolization or by Seitz-filtration of oxalated plasma. Thus, aged normal plasma and aged Dicumarol plasma, and normal and Dlcumarol serums were deficient in the labile factor. Another factor, the stable factor, is characterized by its marked stability at refrigerator or room temps., by being readily adsorbed by Seitz-filtration, and by being significantly reduced by the admn. of Dicumarol. The stable factor was found to be deficient in Seitz-filtered normal plasma as well as in Dicumarol plasma and its derivatives: aged Dicumarol plasma, Seitz-filtered Dicumarol plasma, and Dicumarol serum. A deficiency of either the labile or stable factor, with the resultant slowed prothrombin convertibility, could be corrected by adding a serum or plasma which contained the deficient factor. The rate with which prothrombin converts to thrombin would seem to be a function of these accessory factors exclusively, for when normal plasma was mixed with purified prothrombin in various proportions, the conversion rate was independent of the prothrombin concn., but paralleled directly the concns. of the accessory factors.

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