Heterogeneity of Volume-sensitive Chloride Channels in Basolateral Membranes of A6 Epithelial Cells in Culture |
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Authors: | U Banderali J Ehrenfeld |
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Institution: | (1) CEA and CNRS (URA 1855), Laboratoire Jean Maetz. B.P. 68, La Darse. 06230, Villefranche-sur-mer, France, FR |
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Abstract: | A new technique allowing single-channel patch-clamp recordings from basolateral membranes of A6 renal epithelial cells in
culture was developed. Using this technique we studied the chloride channels activated in these basolateral membranes during
hypo-osmotic stress. Four different types of channel were identified and classified according to their current/voltage (I/V) relationships as observed in the on-cell configuration of the patch-clamp technique. Three of these channels had linear
I/V relationships with unitary conductances of 12, 30 and 42 pS. The fourth type had an outwardly rectifying I/V curve with inward and outward conductances of 16 and 57 pS respectively. The kinetic properties of each class of channel
were studied and kinetic models developed for two of them: the 42 pS channel and the outward rectifier. These models permitted
the study of the evolution of the kinetic parameters during hypo-osmotic shock and revealed two different kinetic schemes
of channel activation. The results of experiments made on the basolateral membranes were also compared with those of a set
of analogous patch-clamp experiments carried out on isolated A6 cells. In these latter, the frequency of successful observations
of active channels in a patch was 13%, whereas it was 31% for basolateral membranes. Also, of the four types of channel observed
in basolateral membranes, two were never found in isolated cells, only the 12 pS channel and the outward rectifier were present
in these isolated cells.
Received: 17 April 1996/Revised: 26 June 1996 |
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Keywords: | : Chloride channels — Basolateral membranes — Volume regulation — Hypo-osmotic shock — Patch clamp — Epithelial cells — Isolated cells |
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