長期ワーファリン服用患者におけるプロティンＣおよびビタミンＫ依存性凝固因子の動態

Abstract

Plasma levels of vitamin K-dependent coagulation factors (factors II, VII, IX and X) and protein C were measured in 100 specimens from patients on long-term warfarin therapy. Thrombotest values ranged from 7 to 50%. Both clotting activities and antigens of vitamin K-dependent coagulation factors decreased, depending on thrombotest values. The clotting activity levels of these factors were below their antigen levels, indicating the presence of circulating, inactive molecules ( PIVKAs). The activity to antigen ratios of these factors were correlated with thrombotest values, suggesting that the concentration of PIVKAs relative to normal molecules increases with increasing intensity of anticoagulation. Although protein C antigen was also decreased, the ratios of protein C antigen to factors II, VII, IX and X antigens remained constant, being independent of the intensity of warfarin therapy. These results indicate that long-term oral anticoagulant therapy results in the suppression of the synthesis of both vitamin K-dependent coagulation factors and protein C, and that the production of the coagulant and anticoagulant proteins is, on the whole, well-balanced. In addition, a considerable variation in the levels of protein C antigen was observed among individuals with a similar intensity of anticoagulation.