The Ca2+-sensitive K+ transport in inside-out red cell membrane vesicles.

Ca2+-sensitive K+ transport ("Gárdos-effect") was investigated in inside-out red cell membrane vesicles (IOVs) by measuring the effect of Ca2+ and other agents on the 86Rb+ (K+-analogue) influx. 50 micro M-5 mM Ca2+ stimulated the 86Rb+ influx as compared to the effect of 1 mM EDTA. Mg2+ and chlorpromazine inhibited the effect of Ca2+, oligomycin and quinine were without effect. The permeability increase of K+, elicited by Ca2+ in IOVs, corresponded to that of intact cells. The effect of Ca2+ was not specific to K+ with respect to Na+. The Ca2+-sensitive K+ channels saturated about 5-10 mM KCl in the medium. The results indicate that IOVs the Ca2+-sensitive K+ transport has altered characteristics as compared to that of intact cells and resealed ghosts. However, in contrast to the suggestion of other investigators, it was found that some features of this phenomenon are still preserved in IOVs.