Roka-Moiia Y. Regulation of platelet aggregation by plasminogen/plasmin system.

Object: plasminogen/plasmin system and human platelets. Aim: to clarify the role of the components of plasminogen/plasmin system in regulation of platelet aggregation and to establish the regularities of plasminogen activation with platelet participation. Methods: preparative biochemistry, chromatography, defining of enzyme activity, spectroscopy, gel-electrophoresis, immunoblotting. It was proved that plasminogen/plasmin system regulates the functional state of platelets. Lys-plasminogen, which can be formed on the platelet surface, possesses the potent antiaggregatory effect and prevents agonist-induced reorganization of actin cytoskeleton of platelets. Antiaggregatory effect of Lys-plasminogen is due to its two-centered interaction through lysine-binding sites of its kringle domains with platelet membrane-associated proteins, which are exposed during the activation and take part into aggregation. It was established that platelets are involved into regulation of activity of plasminogen/plasmin system. They promote plasminogen activation and local plasmin generation. At the same time platelets accumulate and release the essential amount of active plasminogen activator inhibitor-1, which can efficiently inhibit plasminogen activation.