Determinants of coagulation activation in humans.
To evaluate the mechanism responsible for the generation of factor VIIa in vivo, we measured the levels of this enzyme after administering purified factor IX concentrates to patients with hemophilia B. Their factor VIIa levels were initially very low and gradually increased to normal, but there were no significant changes in the generation of factor Xa or thrombin. The administration of 10 mu g/kg body weight of recombinant factor VIIa to patients with factor VII deficiency increased the circulating levels 35-fold, but this only resulted in normalization of the activation of factor IX and factor X. Our data indicate that factor IXa is primarily responsible for the basal levels of free factor VIIa in vivo, and that changes in free factor VIIa in the blood do not necessarily lead to alterations in factor X activation.
Hematology-Oncology Section, Department of Medicine, Brockton-West Roxbury Department of Veterans Affairs Medical Center, Massachusetts 02132, USA.
K A
KA
Bauer
S
S
Eichinger
P M
PM
Mannucci
R D
RD
Rosenberg
D005164:Factor IX / Q000627:therapeutic use*; D015942:Factor VIIa / Q000378:metabolism*; D002836:Hemophilia B / Q000097:blood / Q000188:drug therapy*; D006801:Humans; D013925:Thromboplastin / Q000502:physiology
D005164:Factor IX; D013925:Thromboplastin; D015942:Factor VIIa