Involvement Of Human Factor IX In Tissue Thromboplastin Induced Coagulation

Abstract

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.

Activation of Human Coagulation Factor VIII by Activated Factor X, the Common Product of the Intrinsic and the Extrinsic Pathway of Blood Coagulation

“…Our own experiments (see Table 1) and those of others (28,31) indicate that the time interval used to follow factor Xa generation is much longer than that needed for plasma coagulation. In this respect it is interesting that Van den Besselaar et al (15) reported that even at extremely low tissue factor concentrations the plasma-coagulation time is independent on the presence or absence of the intrinsic activator (factor VffI, factor D(). Flowever, at present it is still questionable which model glves the better approximation of in vivo coagulation: the generation of activated coagulation factors or plasma coagulation times.…”

The Role of Factor IX in Tissue Thromboplastin Induced Coagulation

“…Thromboplastin concentration was varied by recombination of different amounts of apoprotein with a constant amount of phospholipid. Part of this study has been reported earlier in a preliminary form (6).…”