ROS activate KCl cotransport in nonadherent Ehrlich ascites cells but K+ and Cl- channels in adherent Ehrlich Lettré and NIH3T3 cells.
Addition of H(2)O(2) (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 H(2)O(2)-induced cell shrinkage was unaffected by the presence of clofilium and clotrimazole, which blocks volume-sensitive and Ca(2+)-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 H(2)O(2)-induced cell shrinkage was impaired in the presence of the KCl cotransport inhibitor (dihydro-indenyl)oxyalkanoic acid (DIOA), following substitution of NO(3)(-) for Cl(-), and when the driving force for KCl cotransport was omitted. It is suggested that H(2)O(2) activates electroneutral KCl cotransport in Ehrlich ascites tumor cells and not K(+) and Cl(-) channels. Addition of H(2)O(2) 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 H(2)O(2) on cell volume was blocked by the serine-threonine phosphatase inhibitor calyculin A, indicating an important role of serine-threonine phosphorylation in the H(2)O(2)-mediated activation of KCl cotransport in Ehrlich cells. In contrast, addition of H(2)O(2) 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, H(2)O(2) induces KCl cotransport or K(+) and Cl(-) channels in nonadherent and adherent cells, respectively.
Dept. of Biology, The August Krogh Building, Universitetsparken 13, DK-2100, Copenhagen Ø, Denmark. ihlambert@bio.ku.dk
Ian Henry
IH
Lambert
Thomas Kjaer
TK
Klausen
Andreas
A
Bergdahl
Charlotte
C
Hougaard
Else Kay
EK
Hoffmann
D000818:Animals; D002264:Carboxylic Acids / Q000494:pharmacology; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D048429:Cell Size; D018118:Chloride Channels / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D007038:Hypotonic Solutions; D007192:Indenes / Q000494:pharmacology; D017136:Ion Transport; D008387:Marine Toxins; D051379:Mice; D041681:NIH 3T3 Cells; D009566:Nitrates / Q000378:metabolism; D009997:Osmotic Pressure; D010080:Oxazoles / Q000494:pharmacology; D018384:Oxidative Stress; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D015221:Potassium Channels / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D027981:Symporters / Q000378:metabolism*; D013997:Time Factors; D000096922:K Cl- Cotransporters
D002264:Carboxylic Acids; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D006861:Hydrogen Peroxide; D007038:Hypotonic Solutions; D007192:Indenes; D008387:Marine Toxins; D009566:Nitrates; D010080:Oxazoles; D010749:Phosphoprotein Phosphatases; D015221:Potassium Channels; D017382:Reactive Oxygen Species; D027981:Symporters; D000096922:K Cl- Cotransporters; C059990:((dihydroindenyl)oxy)alkanoic acid; C059041:calyculin A