| Abstract: | The effect of Ca2+ on the electric potential and permeability of human erythrocyte membranes for K+ was investigated. An increase of K+ concentration in a medium containing a Ca-ionophore A 23187 causes hyperpolarization of the erythrocyte membrane (by 50-60 mV) due to a 70-fold increase of its permeability for K+ (K0.5 for Ca2+ in both cases is equal to 2-3 microM). Using calmodulin-deficient inside-out erythrocyte membrane vesicles, it was demonstrated that regulation of the transmembrane potentials by Ca2+ is mediated by its interaction with calmodulin (K0.5 for Ca2+ and calmodulin is equal to 2-3 microM and 100-150 nM, respectively). It was assumed that the Ca2+-calmodulin complex is involved in the functioning of the plasma membrane K+-channel. |
