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XB-ART-29958
J Membr Biol 1984 Jan 01;801:81-9.
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Single-channel recordings of apical membrane chloride conductance in A6 epithelial cells.

Nelson DJ , Tang JM , Palmer LG .


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The apical membrane of epithelial cells from the A6 cell line grown on impermeable substrata was studied using the patch-clamp technique. We defined the apical membrane as that membrane in contact with the growth medium. In about 50% of the patches, channels with single-unit conductances of 360 +/- 45 pS in symmetrical 105 mM NaCl solutions, and characteristic voltage-dependent inactivation were observed. Using excised membrane patches and varying the ionic composition of the bathing medium, we determined that the channels were anion selective, with a permeability ratio for Cl- over Na+ of about 9:1, calculated from the reversal potential using the constant-field equation. The channel was most active at membrane potentials between +/- 20 mV and inactivated, usually within a few seconds, at higher potentials of either polarity. Reactivation from this inactivation was slow, sometimes requiring minutes. In addition to its fully open state, the channel could also enter a flickering state, which appeared to involve rapid transitions to one or more submaximal conductance levels. The channel was inhibited by the disulfonic stilbene SITS in a manner characteristic of reversible open-channel blockers.

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References [+] :
Blatz, Single voltage-dependent chloride-selective channels of large conductance in cultured rat muscle. 1983, Pubmed