Effects of calcium permeabilization on RBC rheologic behavior

Although many RBC rheological properties have been previously described in detail, the biochemical mechanisms leading to premature destruction of red blood cells are less clear. However, several biochemical processes have been suggested as possible mechanisms for membrane structural alterations (e.g., crosslinking of membrane proteins, oxidant damage, binding of cytoplasmic proteins, and altered intracellular ion composition). We have carried out a series of studies aimed at evaluating the effects of calcium-regulated membrane-bound hemoglobin (Hbm) on RBC and derived ghost rheologic behavior. Intracellular calcium was elevated by 10 microM A23187, with cell deformability determined via the Cell Transit Analyzer (CTA). Our results indicate: 1) Linear, positive correlations between Hbm and average RBC rigidity and 2) a marked influence of heterogeneous calcium concentration on both Hbm and rheologic properties for various subpopulation. These findings therefore suggest the importance of hemoglobin-membrane interactions as a determinant of erythrocyte deformability, and may be relevant to RBC aging as well as to diseases such as sickle cell anemia, hereditary spherocytosis and thalassemia.