Increased adsorption of high molecular weight kininogen to heparin-coated artificial surfaces and correlation to hemocompatibility

During the past 10 years investigations have demonstrated that heparin-coat ed devices used for extracorporeal circuits show an improved hemocompatibil ity. We investigated the pathway of adsorption of plasma proteins at hepari n-coated artificial surfaces and the further activation of the humoral and cellular defense mechanisms of the blood. Twenty milliliters of fresh human blood (1 IU heparin/ml) filled a 50 cm long tubes (with and without covale nt heparin-coating), prepared as an in vitro "Closed-Loop'' model and recir culated at a temperature of 37 degrees C, After 5, 15, 30, 60 and 120 min f ibrinogen and high molecular weight kininogen (HMWK) adsorption was measure d by a newly developed modified ELISA technique. In addition, changes in co agulation and platelet activation were measured by well established assays. High concentrations of fibrinogen were detected after very short blood mat erial contact, both on uncoated as well as heparin-coated tubes. However, h igh amounts of HMWK were only found on the heparin-bonded surfaces. In addi tion, the concentrations of the soluble coagulation marker prothrombin frag ment F1+2 and the marker for platelet activation beta-thromboglobulin were significantly higher in the non-coated tubes. We presume that adsorption of HMWK to heparin-coated surfaces contributes to the improved hemocompatibil ity of these bondings. (C) 1999 Elsevier Science B.V. All rights reserved.