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Cell volume-sensitive Na+-ATPase activity in rat kidney cortex cell membranes
F Proverbio1, J A Duque, T Proverbio
1Centro de Biofísica y Bioquímica, Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela.
Biochimica Et Biophysica Acta
|June 7, 1988
Summary
Rat kidney cells possess a unique sodium pump, distinct from the standard Na+/K+ pump. Cell swelling significantly boosts this ouabain-insensitive Na+-ATPase activity, which returns to normal upon volume recovery.
Area of Science:
- Nephrology
- Cell Physiology
- Biochemistry
Background:
- A ouabain-insensitive, K+-independent sodium pump exists in kidney proximal tubular cells, distinct from the ouabain-sensitive Na+/K+ pump.
- The regulation of this unique sodium pump's expression and activity remains largely uncharacterized.
Purpose of the Study:
- To investigate the modulation of the ouabain-insensitive Na+-ATPase (sodium pump) biochemical expression by cell volume in rat kidney proximal tubular cells.
Main Methods:
- Isolation of basolateral plasma membranes from control and swollen rat kidney proximal tubular cells.
- Assay of ouabain-insensitive Na+-ATPase activity in isolated membrane fractions.
Main Results:
- Swollen rat kidney proximal tubular cells exhibited a tenfold increase in basolateral ouabain-insensitive Na+-ATPase activity compared to control cells.
- Upon recovery of normal cell volume, the ouabain-insensitive Na+-ATPase activity decreased significantly, returning to control levels.
- The ouabain-sensitive Na+/K+-ATPase activity remained unaffected by changes in cell volume.
Conclusions:
- Cell volume plays a crucial role in modulating the biochemical expression of the ouabain-insensitive Na+-ATPase in rat kidney proximal tubular cells.
- This volume-dependent regulation highlights a distinct functional adaptation of this unique sodium pump in response to cellular hydration status.