Effect of Plasma and Cellular Factors on the Aggregation of Erythrocytes from Different Age Populations

Microrheologic properties (aggregation and deformability) were examined in young (upper fraction) and old (bottom fraction) erythrocytes separated by density gradient centrifugation at 30000 g. A significant difference in microrheologic properties of the young and old erythrocytes was revieled. Erythrocyte aggregation was studied in the plasma and serum. Aggregation of the young and old cells in plasma was higher than in serum, which points to the importance of the presence of fibrinogen in the aggregation medium. The study of aggregation kinetics showed that the absence of fibrinogen in the medium produced an insignificant effect on the rate of aggregate formation, but it dramatically affected the degree of aggregation (12 and 88% difference between aggregate number in the plasma and serum, respectively). In young erythrocytes, the difference of the degree of aggregation and kinetics of aggregate formation in the plasma and serum was not so pronounced (32 and 43%, respectively). Analysis of correlations between aggregation and deformation of the young and old erythrocytes revealed more pronounced interrelations of these parameters in the plasma compared to serum, indicating an important role of fibrinogen for the manifestation of microrheologic properties of erythrocytes. These interrelations were most pronounced during aggregate formation, which supported the bridging theory of aggregation.