Inhibition of [formula omitted], [formula omitted]-ATPase by ouabain triggers epithelial cell death independently of inversion of the [formula omitted] ratio

Abstract

Treatment with ouabain led to massive death of principal cells from collecting ducts (C7-MDCK), indicated by cell swelling, loss of mitochondrial function, an irregular pattern of DNA degradation, and insensitivity to pan-caspase inhibitor. Equimolar substitution of extracellular Na + by K + or choline + sharply attenuated the effect of ouabain on intracellular Na + and K + content but did not protect the cells from death in the presence of ouabain. In contrast to ouabain, inhibition of the Na +/K + pump in K +-free medium increased Na + i content but did not affect cell survival. In control and K +-free medium, ouabain triggered half-maximal cell death at concentrations of ∼0.5 and 0.05 μM, respectively, which was consistent with elevation of Na +/K + pump sensitivity to ouabain in K +-depleted medium. Our results show for the first time that the death of ouabain-treated renal epithelial cells is independent of the inhibition of Na +/K + pump-mediated ion fluxes and the [Na +] i]/[K +] i ratio.