Influence of Ca2+ on red cell deformability and adaptation to sphering agents.

The following results indicate the close connection between Ca2+ and red cell deformability: ATP-depleted red cells have a lowered deformability, but chlorpromazine and papaverine return the deformability to normal despite unchanged low ATP-concentrations of the cells. Both drugs are known to displace membrane-bound calcium. Without significantly decreasing red cell ATP-content, the calcium-ionophore A23187 reduces the deformability in the presence of 10(-4) to 10(-3) mol external calcium. The ionophore is ineffective in reducing the red cell deformability when the cells are suspended in a calcium-free medium. The sphering agent lysolecithin is less effective in reducing red cell deformability, when the external calcium-concentration is kept low. Without lysolecithin external Ca2+ is ineffective in reducing red cell deformability for several h. These results have been interpreted as showing a calcium-induced reduced mobility of the protein moiety in the red cell membrane.