title: Modulation of Na+,K+-ATPase activity is of importance for RVD.
abstract: OBJECTIVE
  This study was performed to examine the role of Na+,K+-ATPase activity for the adaptive response to cell swelling induced by hypoosmoticity, i.e. the regulatory volume decrease (RVD).
  
  
  METHODS
  The studies were performed on COS-7 cells transfected with rat Na+,K+-ATPase. To study changes in cell volume, cells were loaded with the fluorescent dye calcein and the intensity of the dye, following exposure to a hypoosmotic medium, was recorded with confocal microscopy.
  
  
  RESULTS
  Ouabain-mediated inhibition of Na+,K+-ATPase resulted in a dose dependent decrease in the rate of RVD. Total 86Rb+ uptake as well as ouabain dependent 86Rb+ uptake, used as an index of Na+,K+-ATPase dependent K+ uptake, was significantly increased during the first 2 min following exposure to hypoosmoticity. Since protein kinase C (PKC) plays an important role in the modulation of RVD, a study was carried out on COS-7 cells expressing rat Na+,K+-ATPase, where Ser23 in the catalytic alpha1 subunit of rat Na+,K+-ATPase had been mutated to Ala (S23A), abolishing a known PKC phosphorylation site. Cells expressing S23A rat Na+,K+-ATPase exhibited a significantly lower rate of RVD and showed no increase in 86Rb+ uptake during RVD.
  
  
  CONCLUSIONS
  Taken together, these results suggest that a PKC-mediated transient increase in Na+,K+-ATPase activity plays an important role in RVD.
authors.affiliation: Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
authors.forename: R M
authors.initials: RM
authors.lastname: Andersson
authors.forename: O
authors.initials: O
authors.lastname: Aizman
authors.forename: A
authors.initials: A
authors.lastname: Aperia
authors.forename: H
authors.initials: H
authors.lastname: Brismar
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000032:analysis; D048429:Cell Size / Q000187:drug effects / Q000502:physiology*; D002522:Chlorocebus aethiops; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005452:Fluoresceins; D005456:Fluorescent Dyes; D018613:Microscopy, Confocal / Q000379:methods; D009154:Mutation; D009994:Osmolar Concentration; D009995:Osmosis / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D012414:Rubidium Radioisotopes / Q000493:pharmacokinetics; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014162:Transfection
chemical_list: D004791:Enzyme Inhibitors; D005452:Fluoresceins; D005456:Fluorescent Dyes; D012414:Rubidium Radioisotopes; D010042:Ouabain; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium; C007740:fluorexon