Effect of cyclic nucleotides on calcium dependent K+ channels, in human erythrocytes

Abstract

K+ efflux has been analyzed in human erythrocytes incubated in a K+ free medium containing ouabain, bumetanide, CaCl2, and the Ca2+ ionophore A23187.In these conditions, a K+ efflux, which is exponentially dependent on the concentration of A23187 present in the medium, has been observed.This flux is almost completely abolished by either quinine or EGTA, so that, the above K+ efflux has been considered Ca2+ dependent.The effects of cAMP, and cGMP, have been tested on this flux.Ca2+ dependent K+ efflux decreases in presence of millimolar concentrations of cAMP in the medium.The addition of methyl-isobutyl-xanthine to the incubation medium containing cAMP enhances the inhibitory effect of this compound.cGMP also inhibits the Ca2+ dependent K+ efflux.Our results suggest that cyclic nucleotides may modulate the activation of Ca2+ dependent K+ channels in human erythrocytes.