Mechanism of the anticoagulant effect of warfarin as evaluated in rabbits by selective depression of individual procoagulant vitamin K-dependent clotting factors

• Published in: The Journal of clinical investigation 1993-11, Vol.92 (5), p.2131-2140
• Main Authors: ZIVELIN, A, VIJAYA MOHAN RAO, L, RAPAPORT, S. I
• Format: Article
• Language: English
• Subjects: Animals; Anticoagulants - pharmacology; Biological and medical sciences; Blood Coagulation Factors - metabolism; Blood. Blood coagulation. Reticuloendothelial system; Disseminated Intravascular Coagulation - chemically induced; Factor IX - metabolism; Factor VII - metabolism; Factor X - metabolism; Female; Infusions, Intravenous; Medical sciences; Pharmacology. Drug treatments; Protein Precursors - metabolism; Prothrombin - metabolism; Rabbits; Thromboplastin - pharmacology; Vitamin K - metabolism; Warfarin - pharmacology
• ISSN: 0021-9738; 1558-8238
• DOI: 10.1172/JCI116814

We have evaluated the contribution of depression of individual procoagulant vitamin K-dependent clotting factors to the ability of warfarin to protect rabbits against tissue factor-induced coagulation. Mean activities of individual procoagulant factors were determined, in assays with rabbit substrates, for a group of rabbits achieving a protective degree of anticoagulation with warfarin. Values were: factor VII, 12%; factor IX, 7%; factor X, 14%, and prothrombin, 13%. The effect upon tissue factor-induced coagulation of selective immunodepletion of each factor to a comparable level was then evaluated. Immunodepletion of plasma factor X or prothrombin, but not of factor VII or factor IX, protected otherwise normal rabbits against tissue factor-induced coagulation. Next, we determined the effect upon the protection in warfarin-treated rabbits of selectively restoring factor X or prothrombin before infusing tissue factor. When either factor was selectively restored, warfarin's protective effect was abolished. Moreover, selective restoration of prothrombin sensitized warfarin-treated rabbits to coagulation more severe than observed in nontreated control rabbits. One may extrapolate from these data that depression of both factor X and prothrombin are required for warfarin's clinical antithrombotic efficacy and that depression of plasma prothrombin is particularly important.