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Hypotonically activated chloride current in HSG cells
S Fatherazi1, K T Izutsu, R B Wellner
1Department of Oral Biology, School of Dentistry, University of Washington, Seattle 98195.
The Journal of Membrane Biology
|November 1, 1994
Summary
Hypotonic stress activates potassium (K+) and chloride (Cl-) conductances in HSG cells, potentially underlying their regulatory volume decrease (RVD) response. Activation pathways differ, with K+ involving calcium and Cl- requiring intact actin cytoskeleton.
Area of Science:
- Cell Physiology
- Ion Transport
- Membrane Biophysics
Background:
- Hypotonic stress triggers cellular volume regulation mechanisms.
- Understanding ion channel involvement in cell volume changes is crucial for cellular homeostasis.
Purpose of the Study:
- To investigate hypotonicity-induced changes in whole-cell currents and cell volume in HSG cells.
- To identify the specific ion conductances involved in the regulatory volume decrease (RVD) response.
Main Methods:
- Whole-cell patch clamp electrophysiology to measure ion currents.
- Coulter counter technique to assess cell volume changes.
- Pharmacological agents (NPPB, SITS, cytochalasin D) and ionic manipulations were used to characterize currents and RVD.
Main Results:
- Hypotonic solutions induced dose-dependent increases in K+ and Cl- conductances.
- The K+ current was Ca(2+)-activated, while the Cl- current was inhibited by NPPB and SITS, and required ATP and intact F-actin.
- Hypotonic stress induced cell swelling followed by RVD, which was inhibited by combined NPPB and quinine, or by cytochalasin D.
Conclusions:
- Hypotonic stress activates distinct K+ and Cl- conductances in HSG cells, likely mediating the RVD response.
- The K+ conductance pathway involves intracellular calcium, whereas the Cl- conductance pathway is calcium-independent but requires an intact actin cytoskeleton.
- These findings elucidate the ion channel mechanisms underlying cellular volume regulation under osmotic stress.