| Autor: |
O Larm, Jesper Swedenborg, J Risenfeldt, P Olsson, K Kodama, B Pasehe |
| Rok vydání: |
1987 |
| Předmět: |
|
| Zdroj: |
XIth International Congress on Thrombosis and Haemostasis. |
| ISSN: |
2567-689X |
| DOI: |
10.1055/s-0038-1643091 |
| Popis: |
Covalent end-point attachment of heparin fragments (8 000 daltons) to artitifical materials results as published before in a highly thromboresistant surface. Approximately one out of six bonded fragments carry the antithrombin III (AT) binding sequence. i.e. the high affinity site. With regard to thrombin inhibition the heparin surface resembles the endothelium. The present work deals with the uptake on the immobilized heparin and its significance for F Xa inhibition. The uptake of AT was studied at 0.15 M and 0.35 M NaCl concentration (TRIS buffer, pH 7.4) respectively and determined as disappearance of AT activity in the exposed solutions. Large amounts were adsorbed at 0.15 M and the uptake was both concentration and time dependent. At 0.35 M the uptake was the same at all the tested AT concentrations: 5 pico-moles/square cm. It was deduced that mainly high affinity sites had taken up AT at 0.35 M and that both high and low affinity sites had taken up AT at 0.15 M.The non-AT-adsorbed heparin surface did not induce inhibition of F Xa (in TRIS buffer solution) after exposure. The surface AT-adsorbed at 0.15 M induced F Xa inhibition with the same rate in several consecutive exposed aliquots. The surface AT-adsorbed at 0.35 M had a lower inhibitory capacity and only the first F Xa aliquot was inhibited at the same rate as on the surface AT-adsorbed at 0.15 M. The inhibition rate for a second aliquot was slowlier due to the facts that AT had been consumed and that the density of AT on high affinity sites had decreased. It is concluded that AT on high affinity sites determines the rate at which F Xa is inhibited whereas the amount of AT on low affinity sites determines the inhibitory capacity by continously providing the high affinity sites with AT. The migration of AT must take place horizontally in the 100-200 A thick surface layer and may mimic events happening on a cellular membrane with binding sites of different classes for a substance. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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