Abstract
The actions of intracellular pH (pH i ) on Ca2+dependent Cl− channels were studied in secretory epithelial cells derived from human colon carcinoma (T84) and in isolated rat parotid acinar cells. Channel currents were measured with the whole cell voltage clamp technique with pipette solutions of different pH. Ca2+dependent Cl− channels were activated by superfusing ionomycin to increase the intracellular calcium concentration ([Ca2+] i ) or by using pipette solutions with buffered Ca2+ levels. Large currents were activated in T84 and parotid cells by both methods with pH i levels of 7.3 or 8.3. Little or no Cl− channel current was activated with pH i at 6.4. We used on-cell patch clamp methods to investigate the actions of low pH i on single Cl− channel current amplitude in T84 cells. Lowering the pH i had little or no effect on the current amplitude of a 8 pS Cl− channel, but did reduce channel activity. These results suggest that cytosolic acidification may be able to modulate stimulus-secretion coupling in fluid-secreting epithelia by inhibiting the activation of Ca2+-activated Cl− channels.
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The authors thank Mrs. L. Koek for taking care of T84 cells culture. We are grateful to Dr. Tom Gunther for providing fura-2 Kd values at pH levels of 6.4 and 8.3. We thank Dr. Sherrill Spires for a critical reading of the manuscript. This research was supported by a grant from the National Institutes of Health DE09692.
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Arreola, J., Melvin, J.E. & Begenisich, T. Inhibition of Ca2+-dependent Cl− channels from secretory epithelial cells by low internal pH. J. Membarin Biol. 147, 95–104 (1995). https://doi.org/10.1007/BF00235400
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DOI: https://doi.org/10.1007/BF00235400