Evidence of Voltage-induced Channel Opening in Na/K ATPase of Human Erythrocyte Membrane

Previous studies have shown that human erythrocytes when subjected to a high voltage pulsation, in the microsecond time range, lysed in an isotonic medium. The hemolysis was the result of the colloid osmotic swelling, which, in turn, was caused by the voltage perforation of the red cell membranes. In this work we demonstrate that in a low ionic medium at least 35% of the pores was related to the opening of Na+/K4 ATPase channels. The membrane conductance generated by the externally applied electric field could be partially blocked by a specific inhibitor, ouabain, or by a specific cross-linkin g reagent, Cu++-phenanthroline, of the ATPase. The effect of ouabain was saturable and had a mid-point of saturation at 0.15 microM. This value agrees with the physiological inhibition constant of the drug. K+ ion in the external medium suppressed the effect of ouabain, as has also been demonstrated n physiological studies. Experiment presented in this communicaton also suggests that the Na+/K+ ATPase was not perforable in a high ionic medium, and that a large fraction of the voltage-induced pores occurred at as yet unidentified sites.