The Relation between a Naturally Occuring Inhibitor and Prothrombin in Intermediate Product I Formation

Abstract

1. A method for the separation from clotting factors and the concentration of an inhibitor of intermediate product I present in adsorbed plasma and adsorbed serum is described. 2. This inhibitor is not only stable but also activated at 37° C. At 4° C it loses activity. 3. The inhibitory effect on the formation of intermediate product I is counteracted by small amounts of prothrombin or thrombin. 4. After addition of inhibitor prothrombin is necessary for the formation of intermediate product I in the purified system. 5. The discrepancy, in regard to the need for prothrombin (or thrombin) between the purified and the non-purified system can be explained by the relative amounts of inhibitor in the two systems. ^* Investigation carried out during the tenure of a Special Fellowship from the American Heart Institute, United States Public Health Service.