ROS activate KCl cotransport in nonadherent Ehrlich ascites cells but K+ and Cl- channels in adherent Ehrlich Lettre and NIH3T3 cells

Lambert IH, Klausen TK, Bergdahl A, Hougaard C, Hoffmann EK. ROS activate KCl cotransport in nonadherent Ehrlich ascites cells but K+ and Cl- channels in adherent Ehrlich Lettre and NIH3T3 cells. Am J Physiol Cell Physiol 297: C198-C206, 2009. First published May 6, 2009; doi:10.1152/ajpcell.00613.2008.-Addition of H2O2 (0.5 mM) to Ehrlich ascites tumor cells under isotonic conditions results in a substantial (22 +/- 1%) reduction in cell volume within 25 min. The cell shrinkage is paralleled by net loss of K+, which was significant within 8 min, whereas no concomitant increase in the K+ or Cl- conductances could be observed. The H2O2-induced cell shrinkage was unaffected by the presence of clofilium and clotrimazole, which blocks volume-sensitive and Ca2+-activated K+ channels, respectively, and is unaffected by a raise in extracellular K+ concentration to a value that eliminates the electrochemical driving force for K+. On the other hand, the H2O2-induced cell shrinkage was impaired in the presence of the KCl cotransport inhibitor (dihydro-indenyl)oxy-alkanoic acid (DIOA), following substitution of NO3- for Cl-, and when the driving force for KCl cotransport was omitted. It is suggested that H2O2 activates electroneutral KCl cotransport in Ehrlich ascites tumor cells and not K+ and Cl- channels. Addition of H2O2 to hypotonically exposed cells accelerates the regulatory volume decrease and the concomitant net loss of K+, whereas no additional increase in the K+ and Cl- conductance was observed. The effect of H2O2 on cell volume was blocked by the serine-threonine phosphatase inhibitor calyculin A, indicating an important role of serine-threonine phosphorylation in the H2O2-mediated activation of KCl cotransport in Ehrlich cells. In contrast, addition of H2O2 to adherent cells, e. g., Ehrlich Lettre ascites cells, a subtype of the Ehrlich ascites tumor cells, and NIH3T3 mouse fibroblasts increased the K+ and Cl- conductances after hypotonic cell swelling. Hence, H2O2 induces KCl cotransport or K+ and Cl- channels in nonadherent and adherent cells, respectively.