Relationship of inhibition by lactadherin to phospholipid concentration.
The function of factor Xase complex (A) and prothrombinase complex (B) on sonicated vesicles was evaluated at 0.1 (●), 0.5 (■), and 2.5 (▴) μM phospholipid concentrations in the presence of 1.5 mM CaCl2. Function of the factor Xase complex in the absence of phospholipid was also evaluated (♦; C). Inhibition by lactadherin at various concentrations was measured by means of 2-step amidolytic assays for the production of factor Xa (A,C) or thrombin (B) as described in “Materials and methods.” The inhibitory concentration of lactadherin was directly related to phospholipid concentration. In the absence of phospholipid (C), lactadherin was an inefficient inhibitor of the factor Xase complex. Data obtained at various phospholipid concentrations were normalized for comparison of relative inhibition by lactadherin. Phospholipid composition was at a PS-PE-PC ratio of 4:20:76. Data displayed are from a single set of experiments (A-B) or a single experiment representative of 3 experiments (C).
