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Differential effects of tamoxifen and I- on three distinguishable chloride currents activated in T84 intestinal cells
M A Valverde1, G M Mintenig, F V Sepúlveda
1Department of Cellular Physiology, AFRC Babraham Institute, Cambridge, UK.
Abstract:
The whole-cell mode of the patch-clamp technique has been used to monitor ionic currents in T84 colonic carcinoma cells. The cells were stimulated by either a cAMP cocktail, ionomycin or hypotonicity. Sizeable currents with distinct kinetics were observed after the stimulation with the different agonists. These kinetically distinct Cl- currents also presented a differential sensitivity to the anti-oestrogen Tamoxifen and to the halide I-. Tamoxifen only inhibits the volume activated Cl- current without affecting the other two. Substitution of extracellular Cl- by I- shifted the reversal potential towards more negative values both in the hypotonicity and ionomycin activated Cl- currents. The cAMP activated current responded to the Cl- substitution by I- with a blockade of both outward and inward currents, in addition to the displacement of the zero current level towards positive values. Thus, the use of these two simple tools, I- and tamoxifen, allows the distinction of Cl- channels in epithelial cells.
Insights
This study distinguishes chloride channels in T84 cells using patch-clamp electrophysiology. Tamoxifen and iodide ions selectively inhibit distinct chloride currents, aiding in channel identification.
Area of Science:
- Cellular physiology
- Ion channel research
- Gastrointestinal cell biology
Background:
- T84 colonic carcinoma cells are a model for epithelial ion transport.
- Understanding chloride (Cl-) channel function is crucial for epithelial physiology.
- Differentiating between various Cl- currents is essential for accurate physiological studies.
Purpose of the Study:
- To differentiate distinct chloride currents in T84 cells.
- To investigate the differential effects of Tamoxifen and iodide (I-) on Cl- currents.
- To establish simple electrophysiological tools for Cl- channel identification.
Main Methods:
- Whole-cell patch-clamp electrophysiology was employed.
- T84 cells were stimulated with cAMP, ionomycin, or hypotonicity.
- Ionic currents were analyzed for kinetics and sensitivity to Tamoxifen and I-.
Main Results:
- Distinct Cl- currents were observed upon stimulation with different agonists.
- Tamoxifen selectively inhibited the volume-activated Cl- current.
- Extracellular I- substitution differentially affected Cl- currents, aiding in their distinction.
Conclusions:
- Tamoxifen and iodide ions serve as effective tools to distinguish between different Cl- channels in epithelial cells.
- These findings contribute to a better understanding of ion transport mechanisms in the colon.
- The study highlights the utility of simple pharmacological and ionic manipulations for Cl- channel characterization.