Changes in the intracellular Ca2+ content in human red blood cells in the presence of glycerol

Changes of the intracellular Ca2+ content in human red blood cells (RBCs) in glycerol-containing solutions and after freeze–thawing the cells with glycerol and subsequent deglycerolization were investigated with the Ca2+-sensitive fluorescent dye fluo-4 using fluorescence microscopy. In the glycerol-containing solutions the Ca2+ content increased when compared with a physiological medium (Hepes buffered saline solution (HBSS)). This effect was most likely a result of an inhibition of the Ca2+ pump. After inhibiting the Ca2+ pump using o-vanadate, the Ca2+ uptake was not significantly different in the cells in glycerol-containing and physiological medium. Freeze–thawing and deglycerolization of RBCs resulted in a more pronounced increase in the Ca2+ content. Also in this case, the Ca2+ pump seemed to play a major role.