Fig. 3.
hTFAA functions in vitro as an antagonist of membrane bound TF. (A) hTFAA inhibition of FX activation catalyzed by mTF⋅FVIIa. The concentrations of FVIIa, mTF, and FX were 1 nmol/L, 10 nmol/L, and 1 μmol/L, respectively. Rate of FXa generation is shown for 0 (○), 100 nmol/L (▴), 1 μmol/L (▪), and 10 μmol/L (⋅) hTFAA. (B) hTFAA inhibition of relipidated TF(1-243)⋅FVIIa catalyzed activation of FX. For these experiments, the FVIIa concentration was 0.05 nmol/L, the substrate (FX) concentration was 200 nmol/L, and the TF(1-243) concentration was 0.05 nmol/L (⋅), 0.2 nmol/L (▪), 1 nmol/L (▴), or 5 nmol/L (▾). The rate of FXa production in the presence of the indicated hTFAA concentration was measured and is reported as the fraction of the rate observed in the absence of hTFAA. Solid lines are the result of nonlinear regression analysis by using equation 2 yielding the binding constants shown in Table 3.