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This Article Full Text Full Text (PDF) All Versions of this Article: 297/1/C198    most recent 00613.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Lambert, I. H. Articles by Hoffmann, E. K. PubMed PubMed Citation Articles by Lambert, I. H. Articles by Hoffmann, E. K.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

ROS activate KCl cotransport in nonadherent Ehrlich ascites cells but K⁺ and Cl^– channels in adherent Ehrlich Lettré and NIH3T3 cells

¹NeuroSearch A/S, Ballerup, Denmark; ²Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada; ³Department of Biology, The August Krogh Building, University of Copenhagen, Copenhagen, Denmark

Submitted 26 November 2008 ; accepted in final form 4 May 2009

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)oxyalkanoic 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 Lettré 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.

regulatory volume decrease; taurine; reactive oxygen species