Calcium dependence and distribution of calcium-activated chloride channels in Xenopus oocytes

• Published in: The Journal of physiology Vol. 502; no. Pt 3; pp. 569 - 574
• Main Authors: Gomez-Hernandez, J M, Stühmer, W, Parekh, A B
• Format: Journal Article
• Language: English
• Published: Oxford, UK The Physiological Society 01-08-1997; Blackwell Science Ltd
• Subjects: Animals; Calcium - pharmacology; Calcium - physiology; Chloride Channels - physiology; Electric Stimulation; Female; Ion Channel Gating - drug effects; Kinetics; Oocytes - physiology; Patch-Clamp Techniques; Signal Transduction - drug effects; Signal Transduction - physiology; Xenopus; Xenopus laevis
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1111/j.1469-7793.1997.569bj.x

1. The Ca(2+)-dependent Cl- current (ICl,Ca), expressed in the plasma membrane of Xenopus oocytes, was examined in excised
inside-out macropatches using a rapid perfusion system. 2. Application of Ca(2+)-containing Ringer solution resulted in the
activation of a current whose reversal potential shifted to the right by 51 +/- 5.2 mV when Cl- in the pipette solution was
lowered from 119.3 to 10 mM. No currents were generated when Ca2+ was omitted from the solution. The current is therefore
a Ca(2+)-activated Cl- one. 3. Following exposure to Ca2+, the half-time for activation of ICl,Ca was not voltage dependent,
whereas deactivation was strongly so. 4. ICl,Ca was stable in the continuous presence of Ca2+ and showed no sign of inactivation
or adaptation. 5. Comparison of the size of the currents (normalized to pipette resistance) from the animal and vegetal poles
revealed that ICl,Ca had a highly polarized distribution. The current density was almost 10 times higher in the animal pole.
6. The results suggest that Cl- channels provide a continuous and reliable indication of submembranous Ca2+, at least in an
excised patch, and the clustering of the Cl- channels renders it necessary to exert caution in interpreting results involving
the kinetics of Ca2+ signalling, when ICl,Ca is used as the sole monitor of calcium.