Chloride currents inChara—A patch-clamp study

• DOI: 10.1007/bf01871018
• Publication Date: 2005-07-01T22:39:11Z
• Authors: H. A. Coleman
• Keywords: Reversal potential; Current clamp; Hyperpolarization; Chloride channel

Ionic current steps were recorded with the patch-clamp technique from algal cells that had been prepared without enzyme treatment. Inward current steps with different conductance levels occurred, the lowest level being 7 pS. There were complex transitions between levels indicating either a lack of independence between single channels, or sublevels of a much larger conductance unit. The reversal potential was consistent with the permeant ion being Cl−. Furthermore, when a different concentration of Cl− was used in the patch electrode the reversal potential of the inward current shifted in a manner consistent with a Nernstian change in the Cl− reversal potential. The frequency of the current steps was voltage dependent and suggestive of the hyperpolarization-activated Cl− currents reported in voltage-clamp studies. Outward current steps, with conductances of 38 pS, were recorded when the membrane patch was depolarized by more than +120 mV. Their amplitude and frequency increased at more positive potentials. The current was probably carried by an efflux of cations through a different set of channels. The resting membrane potential, measured unambiguously without contamination from the tonoplast, was −190±5 mV.