Ultrastructural alterations in red blood cell membranes exposed to shear stress

In the mechanism of damage to red blood cells (RBCs) caused by a centrifugal pump, the prolonged effects to the RBC membrane caused by exposure to shear stress remain unclear. We focused on the band 3 protein (B3), one of the major proteins in the membrane skeleton, and investigated the ultrastructural alterations of the RBC membrane with loaded shear stress. Using flow cytometry, the relative amount of B3 was examined in relation to RBC deformability. The results, with continuous exposure to low shear stress, showed cell downsizing, an increase in B3 density, and a decrease in the deformability of the RBC membrane. Exposure to high shear stress does not appear to exert any influence on the membrane skeleton of the RBC. Therefore, in addition to conventional processes including the instantaneous destruction of a cell due to intense shear stresses, the results of the present study indicate the presence of another process based on changes in membrane proteins leading to cell fragmentation. Under low shear stress, the RBC membrane skeleton shows delayed destruction, which is exhibited as a disorder of B3 distribution, and the related membrane dysfunction includes decreases in RBC deformability and stability.