THE K-ATP CHANNEL REGULATES THE EFFECT OF CA2+ ON GAP JUNCTION PERMEABILITY IN CULTURED ASTROCYTES

Using the scrape-loading technique me show that tolbutamide and glyben zcyclamide, two inhibitors of the K+ channel sensitive to ATP (K-ATP c hannel), partially prevent the inhibition of gap junction permeability promoted by Ca2+ in cultured astrocytes, This effect was dose-depende nt, reaching a maximum at 400 mu M and 1 mu M of tolbutamide and glybe nzcyclamide, respectively. The presence of the Ca2+ ionophore A-23187 strongly reduced the concentration of Ca2+ required to block gap junct ion permeability but did not abolish the effect of tolbutamide and gly benzcyclamide. These results suggest that the effect of these two comp ounds are not brought about by control of the intracellular concentrat ion of Ca2+ but probably by the promotion of plasma membrane depolariz ation. (C) 1998 Federation of European Biochemical Societies.