Modulation of Na+,K+-ATPase activity is of importance for RVD.
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.
Andersson
R M
RM
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Aizman
O
O
Aperia
A
A
Brismar
H
H
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
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