RETENTION OF THROMBIN BY POLYTETRAFLUOROETHYLENE - INFLUENCE ON THE ADSORPTION OF FIBRINOGEN FIBRIN

Beads of polytetrafluoroethylens were used to investigate adsorption o f thrombin and the influence of the adsorbed protease on a subsequent deposition of fibrinogen. Adsorption of active thrombin was not detect ed by a specific fluorogenic substrate unless > 0.1 units/ml had been applied. Adsorption was considerably improved by albumin, which protec ted soluble thrombin from inactivation by hydrophobic surfaces. Retent ion of active thrombin was optimal at ca. 0.1% albumin and decreased a t higher concentrations. After incubation with plasma, negligible thro mbin activity was detected at the polytetrafluoroethylene beads by the fluorogenic substrate. However, repeated incubation with fresh plasma samples resulted in adsorbed activity rising with each step. This res ult suggested that thrombin activity should also accumulate at a polyt etrafluoroethylene surface in vivo if fresh blood is permanently flowi ng past. Adsorbed thrombin improved the subsequent retention of fibrin ogen, monitored by an antibody technique. Concomitantly, fibrinopeptid es A, AP and AY were, slowly released whilst fibrinopeptide B was not detectable before 24 h.