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K+ conductance activated during regulatory volume decrease. The channels in Ehrlich cells and their possible
M I Niemeyer1, L P Cid, F V Sepúlveda
1Centro de Estudios Científicos (CECS), Valdivia, Chile. miniemeyer@cecs.cl
Summary
Hypotonic cell swelling activates potassium (K+) currents in Ehrlich ascites tumor cells. These volume-sensitive K+ channels, potentially TASK-2, are inhibited by clofilium and may play a role in cell volume regulation.
Area of Science:
- Cell Physiology
- Ion Transport
- Membrane Biophysics
Background:
- Cell volume regulation is crucial for cellular function.
- Hypotonic stress triggers ion fluxes to restore cell volume.
- Potassium (K+) currents are implicated in regulatory volume decrease (RVD).
Purpose of the Study:
- To investigate the characteristics of K+ currents activated by hypotonic cell swelling in Ehrlich ascites tumor cells.
- To identify the specific K+ channels involved in this volume-sensitive current.
- To explore the role of signaling molecules in regulating these currents.
Main Methods:
- Whole-cell patch-clamp technique at 37°C.
- Experiments conducted with buffered intracellular Ca2+ to isolate K+ currents.
- Cation selectivity, current-voltage relationships, and drug inhibition studies.
Main Results:
- Volume-sensitive K+ currents were observed, independent of intracellular Ca2+.
- The selectivity sequence for cations was K+ > Rb+ > NH4+ > Na+ ≈ Li+ ≈ Cs+.
- The drug clofilium blocked the current and inhibited RVD; leukotriene D4 (LTD4) activated the current.
Conclusions:
- Swelling-activated K+ channels in Ehrlich cells exhibit properties of background K+ channels.
- The TASK-2 channel, a member of the 2P-4TM family, is a potential candidate for mediating these currents.
- These findings contribute to understanding the molecular mechanisms of cell volume regulation.