Impact of microparticles derived from erythrocytes on fibrinolysis.

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.