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- Andersson, R. M., et al.
(author)
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Modulation of Na+,K+-ATPase activity is of importance for RVD
- 2004
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In: Acta Physiologica Scandinavica. - 0001-6772 .- 1365-201X. ; 180:4, s. 329-334
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Journal article (peer-reviewed)abstract
- Aim: 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 Rb-86(+) uptake as well as ouabain dependent Rb-86(+) 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 Rb-86(+) uptake during RVD. Conclusion: Taken together, these results suggest that a PKC-mediated transient increase in Na+,K+-ATPase activity plays an important role in RVD.
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- Belusa, R, et al.
(author)
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Changes in Na(+)-K(+)-ATPase activity influence cell attachment to fibronectin
- 2002
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In: American journal of physiology. Cell physiology. - : American Physiological Society. - 0363-6143 .- 1522-1563. ; 282:2, s. C302-C309
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Journal article (peer-reviewed)abstract
- Most vital cellular functions are dependent on a fine-tuned regulation of intracellular ion homeostasis. Here we have demonstrated, using COS cells that were untransfected or transfected with wild-type rat ouabain-resistant Na+-K+-ATPase, that partial inhibition of Na+-K+-ATPase has a dramatic influence on cell attachment to fibronectin. Ouabain dose-dependently decreased attachment in untransfected cells and in cells expressing wild-type Na+-K+-ATPase, but not in cells expressing ouabain-insensitive Na+-K+-ATPase, whereas inhibition of Na+-K+-ATPase by lowering extracellular K+concentration decreased attachment in all three cell types. Thirty percent inhibition of Na+-K+-ATPase significantly attenuated attachment. Na+-K+-ATPase inhibition caused a sustained increase in the intracellular Ca2+concentration that obscured Ca2+transients observed in untreated cells during attachment. Inhibitors of Ca2+transporters significantly decreased attachment, but inhibition of Na+/H+exchanger did not. Ouabain reduced focal adhesion kinase autophosphorylation but had no effect on cell surface integrin expression. These results suggest that the level of Na+-K+-ATPase activity strongly influences cell attachment, possibly by an effect on intracellular Ca2+.
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