title: A simplified PTT-based protein C activity assay using the thrombin-thrombomodulin complex.
abstract: A simplified assay for protein C activity in plasma is described which uses the ability of rabbit lung thrombomodulin to inhibit the procoagulant activity of thrombin while stimulating protein C activation. Barium eluates of plasma are activated for one hour at 37 degrees C by a mixture of human thrombin and rabbit lung thrombomodulin at concentrations which neutralize each other's effect on the kaolin-cephalin activated partial thromboplastin time (PTT). Protein C anticoagulant activity in the activated eluates is then measured directly in the PTT. The method is independent of protein S levels in the test samples, and is suitable for warfarinized and heparinized plasma. Protein C levels obtained with this method correlate closely with functional levels of vitamin K-dependent procoagulants as measured by the prothrombin and proconvertin time (P&P) in normal subjects and in patients receiving warfarin, indicating specificity for gamma-carboxylated protein C. The method has the potential to detect molecular variants defective in any of the interactions required for generation of anticoagulant activity in vivo.
mesh_terms: D001780:Blood Coagulation Tests; D006023:Glycoproteins / Q000097:blood*; D006801:Humans; D008722:Methods; D010314:Partial Thromboplastin Time; D011486:Protein C; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D013917:Thrombin; D014859:Warfarin / Q000627:therapeutic use
chemical_list: D006023:Glycoproteins; D011486:Protein C; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D014859:Warfarin; D013917:Thrombin