Effect of Donor Age on the Deformability and Aggregability of Density-Separated Red Blood Cells.

Deformability of density-separated red blood cells (RBC) was determined in individuals, in three different age groups. The "young" group was composed of eight individuals between 22-30 years of age; there were eight individuals between 35-45 years of age in the "mid-age" group and 8 individuals between 60-85 years of age in the "old" group. Density separation was performed using discontinuous, Iodixanol (Optiprep®) density gradients. Five layers of Iodixanol with densities between 1.075 and 1.115 g/mL were used. The density distribution of RBC was estimated by determining the hemoglobin concentration in each layer, after centrifugation. The RBC deformability was measured by ektacytometry in least and most dense RBC fractions. In all age groups, the RBC were mostly accumulated in the layers with 1095 and 1105 g/mL densities. In the "young" group, about 80% of RBC were distributed in each of these gradients almost equally. In the "old" group, 50% of RBC were in 1095 g/mL density layer, while 28% was present in the 1105 g/mL layer. The values for "mid-age" group were in between "young" and "old" groups. In all age groups, EI of denser RBC were smaller, in comparison with the RBC in less dense layers. However, the difference between the EI of less and more dense RBC was more pronounced in the "old" group. RBC aggregation was found to be higher in denser RBC fraction, but the difference was less pronounced in "old" group. These results suggest that, RBC circulating in the vasculature of "aged" individuals exhibit more pronounced rheological alterations, during the aging process of RBC.