Inhibition of thrombin generation by ZPI.

Mixtures containing PZ (40 nmol/L), ZPI (69 nmol/L), phospholipids (15 μmol/L), CaCl₂ (4 mmol/L), and factor V or Va (6 nmol/L) in HSA were incubated for 2 minutes at room temperature. Prothrombin (1.4 μmol/L) and factor Xa (0.1 nmol/L) were then added in succession to initiate the reaction. Thrombin activity was determined by amidolytic assay. (A) Mixtures containing factor V. (B) Mixtures containing factor Va. ●, without PZ, without ZPI; ▪, with PZ, without ZPI; ▴, without PZ, with ZPI; ▾, with PZ, with ZPI; ♦, factor Xa preincubated with PZ, ZPI, factor Va, phospholipids, and CaCl₂ prior to the addition of prothrombin.