Volume control of erythrocytes during storage. The role of mannitol

Abstract

When red cells are stored as suspensions in artificial preservative solutions such as those consisting of saline, adenine, and glucose, increased hemolysis of the red cells occurs in vitro, a phenomenon that is readily prevented by the addition of mannitol. The mechanism by which mannitol prevents hemolysis is unknown. The authors have examined the possibility that mannitol prevents hemolysis by prevention of osmotic swelling of red cells that might otherwise increase their volume beyond their critical hemolytic volume. Storage in artificial media does, indeed, result in swelling of the red cells, which is prevented by mannitol and is increased by the addition of nystatin, an agent that greatly increases the sodium-potassium permeability of the cells. Swelling and hemolysis are correlated at different concentrations of mannitol, but the correlation breaks down when the case of nystatin-treated cells is considered; even with marked swelling, there is relatively little hemolysis. Moreover, increasing the volume of the stored red cells acutely by osmotic means results in relatively little additional hemolysis. These findings make it appear unlikely that simple osmotic lysis is the cause of hemolysis in stored cells. Some other stabilizing effect of mannitol that may or may not be related to its osmotic effect must play a role.