ИСТИНА

Aggregation of red blood cells (RBC) and platelets is one of key factors, which determines the blood flow and thereby affects the blood rheology and microcirculation. Alterations in these properties lead to changing the blood viscosity and, as a consequence, to changes in blood flow through vessels and capillaries. This can lead to significant impairment of blood function. Aggregation of RBCs and platelets are commonly known to be dependent on the concentration of vital plasma proteins. The exact role of each plasma protein in platelets aggregation and especially in RBC aggregation is still not well understood. Sometimes the experiments conducted using different techniques with whole blood samples or RBC/platelets suspensions containing mixtures of different plasma proteins yield somewhat controversial results [1]. We assumed that there might be an unaccounted synergetic effect of proteins (e.g. interference between proteins) on cells aggregation [2]. The aim of this work was to assess the kinetics of RBC interaction in vitro in samples with varying plasma proteins (fibrinogen, albumin, gamma globulin, C-reactive protein) and their concentrations by direct measurement of cells interaction forces on cellular level as well as to obtain RBC and platelets aggregation properties in whole blood and plasma samples on large ensembles of the cells. In this work for measurements on ensembles of RBC and platelets we used diffuse elastic light scattering and turbidimetry technique accordingly. To measure pair aggregation of RBC we performed the experiment with optical tweezers. These methods are widely used to measure several parameters that characterize the RBC and platelets aggregation properties in blood. In the paper, we demonstrate the physical foundations of these methods [3] and the results of in vitro measurements of the indices and rate of RBC and platelets aggregation, hydrodynamic strength, characteristic time of formation of RBC aggregates, forces, and aggregation in environment with different plasma proteins. We found that albumin in plasma changes its role from agonist to inhibitor of RBC aggregation with increasing the concentration of fibrinogen. When the concentration of fibrinogen is relatively high, an increase in albumin concentration does not increase the aggregation force but weakens the binding force between the RBCs. Furthermore, a model solution including five major aggregation-inducing proteins yields a weak aggregation force that can hardly be measured. These results indicate that there is an apparent interference among various plasma proteins involved in RBC aggregation and that the synergetic effect of plasma proteins determines the degree of RBC aggregation as well as the aggregation and disaggregation forces. Possible underlying mechanisms of the observed synergetic effects could be due to a change in the RBC and platelets membrane potential or formation of albumin-fibrinogen complexes preventing strong RBC aggregation. These ideas require further studies. To find possible ways of correction of an enhanced aggregation that may be observed in such pathologies as arterial hypertension and diabetes mellitus [3, 4] the studies of the effect of several commonly used inhibitors (RGDS, eptifibatide, tirofiban) on RBC aggregation were performed with blood samples. The hypothesis that cells aggregation can be corrected (reduced) in arterial hypertension by integrin IIb/IIIa glycoproteins (IGP) inhibition of fibrinogen adsorption on RBC membrane was verified experimentally. IGP reduces nonspecific binding of fibrinogen molecules to cell membranes, which results in decreasing molecular bridging between interacting cells. This work was supported by the Russian Science Foundation (Grant No. 22-15-00120).