Comparison of the effect of DHG and LMWH on factor X activation by the intrinsic tenase complex. Increasing concentrations of DHG (•) or LMWH (○) were added to a reaction containing final concentrations of 1.0 nM factor VIIIa, 0.2 nM factor IXa, 200 nM factor X, and 50 μM PC/PS vesicles (75:25) in 0.15 M NaCl, 20 mM HEPES (pH 7.4), 2 mM CaCl₂, 1 mg/mL BSA, and 0.1% PEG-8000. The rate of factor X activation (% control) by the intrinsic tenase complex was determined as described in “Materials and methods.” Mean values were plotted with error bars representing ± SD (n = 3 to 4). The inhibition constants (K_i) for DHG and LMWH were determined by fitting the data by nonlinear regression to the equation for partial, noncompetitive inhibition. K_i values ± SE for DHG and LMWH were 2.2 ± 0.2 and 112 ± 21 nM, respectively.