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.