For many pathological states it is shown that microparticles are one of the hypercoagulation factors. However it isn't clear for what mechanisms they influence on coagulation. Microparticles are able to provide a phospholipid surface for an assembly of complexes of the factors of coagulation necessary for propagation of coagulation in space. Also microparticles are able to initiate coagulation by a contact activation pathway. Platelets also can influence on a phase of propagation and a phase of initiation. The question of the activity of the natural microparticles circulating in plasma against the background of platelets wasn't investigated earlier. For the assessment of the phase of propagation in the test of thrombin generation coagulation was activated by XIa factor, this statement allowed to allocate a contribution of platelets and MP only as surfaces for the assembly of complexes. Direct check of the influence of high concentrations of MP on coagulation propagation was made in the heterogeneous Thrombodynamics-4D test. For assessment of the work of microparticles as activators of coagulation in the test of thrombin generation they were added to plasma together with excess of artificial phospholipid vesicles without an additional activator. In the Thrombodynamics-4D test the contribution to the phase of initiation was determined by the time of the beginning of formation of spontaneous clots and by the amount of their centers of formation. It was shown that microparticles in normal concentration against the background of physiological concentration of platelets don't make a significant contribution to a phase of propagation. With increasing concentration of microparticles in 10 and more times as a result of pathology their role as surfaces for the assembly of complexes remains insignificant, but the activation from microparticles can bring to formation of the new centers of coagulation for the times about ten minutes.
microparticles, hypercoagulation, the contact activation pathway, platelets
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