It has long been known that negatively charged membranes of erythrocyte-derived microparticles display procoagulant activity. However, relatively little is known about the possible fibrinolytic activity of such microparticles. This issue becomes particularly important during red blood cell storage, which significantly increases the number of microparticles. Whole blood was collected from 30 healthy donors. Microparticles were isolated on days 7, 14, 21, and 28 of erythrocyte storage. The effect of microparticles on the fibrinolytic activity of the donor plasma was determined by coagulation and optical (chromogenic substrate) methods. We demonstrated that erythrocyte microparticles had a prominent fibrinolytic activity which cleaves not only fibrin but also chromogenic substrates. Microparticles present fibrinolytic activity mainly due to the presence of plasminogen on them. Microparticles derived from erythrocytes significantly enhance cleavage of the chromogenic substrate by the streptokinase-plasminogen complex, but to a lesser extent accelerate euglobulin clot lysis time. Erythrocyte-derived microparticles display prominent fibrinolytic activity, which significantly decreases during storage of red blood cells.

Coagulation and optical (based on chromogenic substrate) methods were employed to examine antithrombin activity of erythrocytes and erythrocyte-derived microvesicles isolated days 7, 14, 21, and 28 on erythrocyte storage. The erythrocyte-derived microvesicles decelerated fibrin clot formation from fibrinogen in the presence of exogenous thrombin both with and without heparin. Microvesicles reduced optical density of chromogenic substrate. These data suggest that erythrocyte-derived microvesicles display a prominent antithrombin activity, which significantly increases during erythrocyte storage.

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We studied the effect of erythrocyte microvesicles on various stages of platelet-free autoplasma coagulation process. The erythrocyte microvesicles not only exhibited procoagulant activity, but also produced a pronounced anticoagulant effect by inhibiting fibrin formation process. The effects of microvesicles isolated from erythrocytes after 24- and 48-hour cell storage on plasma coagulation were different. The hemocoagulation effects of the "light" and "heavy" microvesicles were studied.