Inhibition of fibrin-platelet interactions by fibrinogen-degradation fragment D.

Homogenized fibrin induced platelet aggregation and the release of serotonin from human platelets. Fragment D, purified from a plasmin digest of human fibrinogen, inhibited these platelet-fibrin interactions. Using a radiolabeled fragment D, it was possible to demonstrate saturable binding of fragment D to fibrin. Nonlabeled fragment D competed with the radiolabeled fragment D for binding to fibrin. Furthermore, the binding of fragment D to fibrin paralleled its ability to inhibit the fibrin-induced release of platelet serotonin. It is postulated that the inhibitory effect of fragment D on fibrin activation of platelets is due to the binding of fragment D to fibrin. The bound fragment D may cover up or block sites on fibrin that are involved in fibrin-platelet interactions. This would then result in inhibition of the fibrin-induced platelet aggregation and release of platelet serotonin.