Isolation and Some Properties of Fibrinogen from Human Blood Platelets

Abstract

Fibrinogen has been isolated from human blood platelets by stepwise precipitation with ammonium sulfate followed by gel filtration through Sephadex G-150 and chromatography through diethylaminoethyl-cellulose. The isolated protein was homogeneous on disc gel and had electrophoretic properties similar to plasma fibrinogen. In immunodiffusion and immunoelectrophoresis, platelet fibrinogen produced a single precipitin line with antiplatelet serum or antifibrinogen serum which was identical with that of plasma fibrinogen. The protein band in disc electrophoresis or the precipitin line in immunoelectrophoresis could not be detected when platelet fibrinogen was treated with thrombin. These properties of platelet fibrinogen were similar to those of plasma fibrinogen. The sedimentation coefficient and intrinsic viscosity of platelet fibrinogen were lower, indicating a lower molecular weight of platelet fibrinogen compared to plasma fibrinogen. Starch gel electrophoresis of plasmin digest of platelet fibrinogen showed a smaller number of bands, the distribution also being different from that of plasma fibrinogen digest. The rate of reaction as well as the extent of polymerization of platelet fibrinogen with thrombin was significantly lower than that of plasma fibrinogen. Results of disc electrophoresis in the presence of sodium dodecyl sulfate-mercaptoethanol confirmed a lower molecular weight of platelet fibrinogen. It has been concluded that platelet fibrinogen, although sharing some properties of plasma fibrinogen, is structurally different and a smaller molecule.