Some properties of autoprothrombin II-A anticoagulant

Autoprothrombin II-A anticoagulant was isolated from bovine prothrombin. Purified prothrombin was applied to DEAE-cellulose chromatography after incubation with thrombin. Four protein peaks were obtained where the third peak corresponded to the anti-coagulant effect. The fractions under the third peak were pooled together and the anticoagulant effect was evaluated with different methods. From 25,470 +/- 2,800 U of prothrombin, 5,800 +/- 1,400 U of inhibitor were obtained. The inhibitor was found to be most effective at pH 7.2--7.8. In vitro, the inhibitor inhibited the thrombin time and the plasma clotting time highly significantly but had no effect on euglobulin lysis time and fibrin plates. In vivo, when injected into rabbits, the inhibitor effect was also significant on the same tests. The autoprothombin II-A anticoagulant had a protective effect on DIC formation with rabbit brain thromboplastin administration. This protective effect was found to be statistically significant.