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Separate swelling- and Ca2+-activated anion currents in Ehrlich ascites tumor cells
S F Pedersen1, J Prenen, G Droogmans
1Department of Biochemistry, August Krogh Institute, University of Copenhagen, Denmark.
The Journal of Membrane Biology
|June 20, 1998
Summary
Two distinct chloride currents, calcium-activated (ICl,Ca) and swelling-activated (ICl,vol), were identified in Ehrlich ascites tumor cells. These currents exhibit different activation, kinetics, and pharmacological properties, indicating separate physiological roles.
Area of Science:
- Cellular physiology
- Ion channel function
- Membrane transport
Background:
- Ehrlich ascites tumor cells possess complex ion transport mechanisms.
- Understanding chloride currents is crucial for cellular volume regulation and signaling.
Purpose of the Study:
- To investigate and differentiate calcium-activated (ICl,Ca) and swelling-activated (ICl,vol) chloride currents in Ehrlich ascites tumor cells.
- To characterize the activation, kinetics, and pharmacological properties of these distinct currents.
Main Methods:
- Whole cell patch clamp technique was employed to record ion currents.
- Intracellular calcium concentration ([Ca2+]i) was manipulated.
- Cell volume was altered via hypotonic exposure.
- Pharmacological agents were used to inhibit specific currents.
Main Results:
- ICl,Ca activated with increased [Ca2+]i, while ICl,vol activated with cell swelling.
- Both currents showed chloride-dependent reversal potentials and similar anion permeability (I- > Cl- > gluconate).
- ICl,Ca kinetics were voltage-dependent and modulated by [Ca2+]i; ICl,vol kinetics were voltage-dependent and Mg2+-sensitive.
- Distinct pharmacological profiles: ICl,Ca inhibited by niflumic acid, NPPB, and DIDS; ICl,vol inhibited by tamoxifen and unaffected by niflumic acid.
Conclusions:
- Ehrlich ascites tumor cells possess at least two separate chloride currents: ICl,Ca and ICl,vol.
- These currents are differentially activated by intracellular calcium and cell swelling, respectively.
- Their distinct properties suggest specialized roles in cellular function and response to stimuli.
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