Involvement Of Human Factor IX In Tissue Thromboplastin Induced Coagulation

This study is concerned with the question whether activation of factor IX by factor VII - tissue thromboplastin contributes to the rate of plasma coagulation. The protein component of tissue factor was partially purified from human brain. Its molecular weight as deduced from SDS - polyacrylamide gel electrophoresis was about 48,000. Reconstitution of thromboplastin activity was obtained by mixing apoprotein and phospholipids in the presence of Triton X-100 and subsequent removal of Triton by adsorption to Biobeads SM-2. Reconstituted tissue factor greatly accelerated the activation of factor IX by isolated factor VII in the presence of calcium ions. In a contact free system (plasma from a patient with congenital factor XII deficiency; factor XII<0.001 Unit/ml) plasma coagulation times (tc) were determined as a function of apoprotein concentration (at constant phospholipid) both in the presence and absence of factor IX. At high apoprotein concentration tc showed to be independent of factor IX, whereas at low apoprotein concentration the removal of factor IX resulted in a 2 - 3 fold increase of tc. The involvement of the tissue factor - factor VII complex in this phenomenon was evaluated using a specific anti-factor VII serum. The results indicate that activation of factor IX by factor VII - tissue thromboplastin does not significantly contribute to the rate of plasma coagulation.