Effect of sulfated xylans during the interaction of [125I]-thrombin with antithrombin III or heparin cofactor II of human plasma.

[125I]-Labeled thrombin was incubated with human plasma and its interactions with the two plasma protease inhibitors antithrombin III (AT-III) or heparin cofactor II (HC-II) were investigated in the presence of oat spelts xylan sulfate (OSXS), sodium pentosan polysulfate (SP-54), and the results were compared with heparin and dermatan sulfate. Addition of OSXS or SP-54 enhanced the complexation of thrombin with HC-II or with both AT-III and HC-II depending upon the concentration and the duration of the interactions of the sulfated compounds with plasma. During the 30 s interaction, OSXS and SP-54 enhanced both AT-III-thrombin and HC-II-thrombin interaction while heparin was more selective and enhanced only the AT-III-thrombin interaction. However after a 2 min interaction, heparin showed an increase in the HC-II-thrombin interaction at higher concentrations. The complexations of AT-III-thrombin and HC-II-thrombin were reversed in the presence of 200 micrograms/ml of SP-54 during a 30 s interaction or in presence of 100 micrograms/ml of OSXS during a 2 min interaction. The Western blotting method of detecting thrombin showed that during the 10 s interaction, heparin enhanced the thrombin-AT-III complex formation while OSXS enhanced the thrombin-HC-II complex formation.