CATALYTIC ACTIVITY AND PLATELET REACTIVITY OF HEPARIN COVALENTLY BONDED TO SURFACES

  • 1 January 1985
    • journal article
    • research article
    • Vol. 105  (2) , 219-226
Abstract
Heparin was covalently bound to solid substrate surfaces by means of 4 different chemistries. It was coupled to polymethylacrylate (PMA) beads with glutaraldehyde, carbodiimide, or radical polymerization initiated by Ce4+, or to agarose beads with cyanogen bromide. Each of these chemistries produced measurable amounts of surface-bound heparin, which was minamally elutable in contact with plasma. Antithrombin (At) binding by heparinized PMA materials (compared with PMA control beads) ranged from no AT binding for the material heparinized with carbodiimide (PMA-Alb-Hep(EDC)) to 3.6 .mu.g/ml packed beads for the material heparinized by radical polymerization (PMA-MA-Hep). Heparin-like catalytic activity of these materials (assayed by measuring the generation of thrombin-antithrombin complex in plasma) correlated well with the amount of heparin bound, not as well with AT binding capacity. Heparinized agarose, which exhibited a large AT binding capacity (2.2 mg AT/ml of packed gel), had virtually no catalytic activity because of its inability to release thrombin-antithrombin complex from the surface. Platelet interaction with heparinized materials that exhibit high AT binding capacity was reduced by pretreatment with normal plasma but not by pretreatment with AT-depleted plasma. Platelet interaction with heparinized materials with low AT binding capacities was not reduced by pretreatment with normal plasma. Apparently, AT binding by heparin reduces the platelet reactivity of heparinized surfaces.