INACTIVATION OF PURIFIED AUTOPROTHROMBIN I WITH ANTITHROMBIN

Abstract

Autoprothrombin Ic was obtained by activating prothrombin preparations with autoprothrombin C. Autoprothrombin Ip was obtained by activating prothrombin with the use of calcium ions and purified platelet factor 3. Both of these prothrombin derivatives were found to be inactivated by plasma and serum. Autoprothrombin Ic was studied most extensively and was found to be inactivated by purified antithrombin. When antithrombin was first combined to capacity with purified thrombin the power to neutralize autoprothrombin I was almost eliminated. Autoprothrombin II was not destroyed by antithrombin and was found in serum as the main procoagulant. Most likely it is not in plasma. Autoprothrombin Ic, autoprothrombin Ip, autoprothrombin C, and thrombin all have reactive groups that combine with antithrombin. The activity in 1 mg of purified autoprothrombin Ic was neutralized by 50 ml plasma. One milligram of autoprothrombin C was neutralized by 5 ml plasma, and 7 ml plasma was sufficient to neutralize 1 mg of thrombin. Antithrombin IV is regarded as a kinetic effect and not as a substance. From a review of the literature it is concluded that there is no adequate evidence for appreciable quantities of factor VII in serum, or that it occurs in plasma independent of prothrombin.