Summary
The abnormal prothrombin produced in patients under coumarin treatment has been isolated from oxalated plasma. After removal of normal prothrombin by adsorption on to small amounts of barium sulfate, coumarin prothrombin proved to be adsorbable on to larger amounts of barium sulfate. After elution into citrate the coumarin prothrombin was precipitated with ethanol and chromatographed on DEAE cellulose. Using a similar linear gradient than for normal prothrombin, the coumarin prothrombin was eluted ahead of normal prothrombin. Immunological studies performed on chromatographed coumarin prothrombin showed that it shared with normal prothrombin the main antigenic determinants and a complete line of identity was obtained when tested against antihuman normal prothrombin antiserum. On crossed Immunoelectrophoresis the electrophoretic mobility of coumarin prothrombin, unlike normal prothrombin, was not modified by the addition of calcium ions. Coagulation studies revealed that coumarin prothrombin could not be activated by physiological activators whereas conversion to thrombin was possible by non physiological activators such as staphylocoagulase and Echis carinatus venom. The amounts of thrombin generated under staphylocoagulase activation per 100 antigen units were similar to those generated by normal prothrombin. The amounts of thrombin obtained under the action of the venom were less than from normal prothrombin. In addition, the activation of coumarin prothrombin proved to be slower than for normal prothrombin.