TY - JOUR
T1 - In situ-generated Thrombin is the only enzyme that effectively activates factor VIII and factor V in thromboplastin-activated plasma
AU - Pieters, Jean
AU - Lindhout, Theo
AU - Hemker, H. Coenraad
PY - 1989
Y1 - 1989
N2 - We investigated the activation of the nonenzymatic protein cofactors factor VIII and factor V in plasma when coagulation was initiated by thromboplastin. With sensitive bioassays, we were able to measure specifically the generation of activated factor VIII and activated factor V in plasma. Our results showed that when plasma was triggered with a relatively high concentration of thromboplastin, factor VIII and factor V were completely activated at the clotting time of plasma. However, when the generation of thrombin, but not that of factor Xa, was delayed by addition of hirudin to the plasma, factor Va was generated only at the time thrombin generation overcame the hirudin inhibition. In addition, generation of factor VIIIa correlated with thrombin generation and not with factor Xa generation. Furthermore, addition of large amounts of factor Xa to hirudinized plasma did not show detectable factor VIII or factor V activation. We concluded that in plasma activated with thromboplastin the enzyme responsible for activation of factor V and factor VIII is thrombin, not factor Xa.
AB - We investigated the activation of the nonenzymatic protein cofactors factor VIII and factor V in plasma when coagulation was initiated by thromboplastin. With sensitive bioassays, we were able to measure specifically the generation of activated factor VIII and activated factor V in plasma. Our results showed that when plasma was triggered with a relatively high concentration of thromboplastin, factor VIII and factor V were completely activated at the clotting time of plasma. However, when the generation of thrombin, but not that of factor Xa, was delayed by addition of hirudin to the plasma, factor Va was generated only at the time thrombin generation overcame the hirudin inhibition. In addition, generation of factor VIIIa correlated with thrombin generation and not with factor Xa generation. Furthermore, addition of large amounts of factor Xa to hirudinized plasma did not show detectable factor VIII or factor V activation. We concluded that in plasma activated with thromboplastin the enzyme responsible for activation of factor V and factor VIII is thrombin, not factor Xa.
U2 - 10.1182/BLOOD.V74.3.1021.1021
DO - 10.1182/BLOOD.V74.3.1021.1021
M3 - Article
SN - 0006-4971
VL - 74
SP - 1021
EP - 1024
JO - Blood
JF - Blood
IS - 3
ER -