Multiple active forms of thrombin: binding to platelets and effects on platelet function.

The effect of various forms of thrombin on certain platelet functions has been investigated. Partially purified bovine thrombin which is a mixture of multiple active forms of thrombin, was chromatographed to yield molecular species termed alpha-, beta-, and gamma-thrombin, each of which has varying degrees of fibrinogen clotting and esterase activities. A direct correlation was observed between the ability of the different forms of thrombin to clot fibrinogen and to influence platelet function. In general, thrombin with high fibrinogen clotting activity was also a potent inducer of platelet aggregation and the release reaction, while those species with low clotting ability were poor inducers of aggregation and release.