Relationships between erythrocyte aggregation, erythrocyte deformability, hematocrit, plasma viscosity and intracellular free calcium of erythrocyte.

Enhanced erythrocyte aggregation and decreased eryhrocyte deformability are thrombogenetic factors, especially in microcirculation where shear rate is low. The aim of this report is to investigate the relationships between erythrocyte aggregation, erythrocyte deformability, hematocrit, plasma viscosity and intracellular free calcium of erythrocyte. Venous blood samples were taken from resting subjects into Na-citrate. Erythrocytes were suspended in calcium free HEPES buffer. Erythrocyte aggregation was measured at high and low shear rate by using the technique which is based on the increase of light transmission through whole blood that occurs when individual cells aggregate into rouleaux or rouleaux-rouleaux complexes; gaps in whole blood between the cell aggregates produce the increased light transmission. The levels of [Ca2+] i of erythrocytes were measured by using fluorescent Ca2+ indicator, fura-2 acetoxymethyl ester. Plasma viscosity was measured via capillary viscometry and erythrocyte deformability was measured by the method of Reid et al. and whole blood hematocrit by microhematocrit method. Both erythrocyte aggregation and erythrocyte deformability were decreased with increasing plasma viscosity and [Ca2+] i of erythrocyte. Erythrocyte aggregation was enhanced with increasing hematocrit. Thus these behaviors of erythrocytes in microcirculation contribute to formation of microthrombi especially at low shear rates.