Membrane and intracellular modes of sugar-dependent increments in red cell stability

Sugar-dependent increments in red cell stability under osmotic stress can be ascribed to changes either in the membrane or in the intracellular matrix. These two possible modes of action have been tested and characterized. Rheological investigation of membrane-free haemoglobin solutions has shown that D-glucose, but not D-fructose, promotes the formation of a visco-plastic gel structure. Gel strength is a function of glucose concentration, haemoglobin concentration and temperature. The ability of various sugars to promote gel formation correlates with their solution properties. The existence of gel structure reduces K+ and haemoglobin leak from red cells whose membranes were partially destroyed by gamma-radiation. Reduced osmotic swelling in the presence of glucose is also due to gel formation since the glucose effect is lost in resealed red cell ghosts. D-Fructose does not protect red cells against radiation damage; its mode of action in increasing red cell stability under osmotic stress is a membrane effect. Cell sizing using the Coulter Counter has shown that fructose, but not glucose, can increase the maximal volume at lysis. At 50 mM, D-fructose expands the red cell ghost volume by 11.2%; this represents a 7.2% increase in membrane area. Ghost expansion by fructose is fructose concentration dependent (0-100 mM) and is insensitive to temperature variation (0-37 degrees C).