Ouabain exerts cytoprotection by diminishing the intracellular K+ concentration increase caused by distinct stimuli in human leukemic cells

Objectives We tested if modulation of cytosolic K+ levels by ouabain, an inhibitor of Na+/K+‐ATPase, exerts cytoprotection against distinct stressful stimuli in human leukemic cells. Methods The cytosolic K+, Na+ or Ca2+ levels and the cytotoxicity were evaluated by flow cytometry. Key findings Various cytotoxic chemicals and ultraviolet irradiation induced cell death and increased intracellular concentrations of K+, Na+ or Ca2+. Ouabain reduced the cytotoxicity and the elevation of cytosolic levels of K+ but not those of Na+ or Ca2+. Conclusions Our data thus suggest that elevated cytosolic K+ levels are associated with the cytotoxicity in response to distinct stressful stimuli and that ouabain exerts cytoprotection most probably by regulating intracellular K+ levels.