INTERACTIONS OF THROMBIN AND ANTI-THROMBIN-III WITH ARTIFICIAL SURFACES

Thrombin adsorption onto Cuprophane surfaces was shown to be not saturable at thrombin concentrations of up to 1 mg/ml and to give adsorption isotherms distinct from those for four other proteins: albumin, fibrinogen, immunoglobulin G, and antithrombin III. Kinetic analyses suggested two types of binding sites with thrombin-Cuprophane apparent dissociation constants (Kd) of 300 nM and 7190 nM respectively. Data from the competitive adsorption of thrombin on Cuprophane in the presence of albumin and immunoglobulin G at both low and high thrombin concentrations and the absence of such types of adsorption of thrombin on PVC support the concept of the presence of these two types of binding sites on Cuprophane. On the other hand, thrombin-poly(vinyl chloride) interaction resulted in a Langmuir type adsorption. Immunoglobulin G shows higher affinity for poly(vinyl chloride) (Kd = 35 nM) than do the other four proteins (Kd=300-900 nM). A hypothesis that multiple types of binding sites that are specific for certain plasma proteins may exist on various artificial surfaces is proposed. © 1979.