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. 1997 Aug 1;502(Pt 3):569–574. doi: 10.1111/j.1469-7793.1997.569bj.x

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

J M Gomez-Hernandez 1, W Stühmer 1, A B Parekh 1
PMCID: PMC1159529  PMID: 9279809

Abstract

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.

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Selected References

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