Pressure-induced hemolysis of in vivo aged human erythrocytes is enhanced by inhibition of water transport via aquaporin-1

Human erythrocytes are fractionated into young, intermediate, and old cells according to their densities. Pressure-induced hemolysis reflects sensitively membrane perturbations. Therefore, the hemolysis of erythrocytes at 200 MPa was examined using fractionated cells. Pressure-induced hemolysis of old (or in vivo aged) erythrocytes was enhanced, compared with those of young and intermediate cells which showed the same hemolytic values. Flow cytometric analysis showed less fragmentation of old erythrocytes under pressure. Moreover, the water transport through the membrane was suppressed in old erythrocytes than intermediate ones. The low permeability of water in old erythrocytes was confirmed by osmotic hemolysis using a hypotonic buffer. These results suggest that water transport via aquaporin-1 (AQP1) is inhibited in old erythrocytes. As the number of AQP1 molecules remained constant in old erythrocytes, the function of AQP1 may be reduced.