The sensitivity of αβγ rat epithelial Na+ channel (rENaC) to osmotically or mechanically induced changes of membrane tension was investigated in the Xenopus oocyte expression system, using both dual electrode voltage clamp and cell-attached patch clamp methodologies. ENaC whole-cell currents were insensitive to mechanical cell swelling caused by direct injection of 90 or 180 nl of 100-mM KCl. Similarly, ENaC whole-cell currents were insensitive to osmotic cell swelling caused by a 33% decrease of bathing solution osmolarity. The lack of an effect of cell swelling on ENaC was independent of the status of the actin cytoskeleton, as ENaC remained insensitive to osmotic and mechanical cell swelling in oocytes pretreated with cytochalasin B for 2–5 h. This apparent insensitivity of ENaC to increased cell volume and changes of membrane tension was also observed at the single channel level in membrane patches subjected to negative or positive pressures of 5 or 10 in. of water. However, and contrary to the lack of an effect of cell swelling, ENaC currents were inhibited by cell shrinking. A 45-min incubation in a 260-mosmol solution (a 25% increase of solution osmolarity) caused a decrease of ENaC currents (at −100 mV) from −3.42 ± 0.34 to −2.02 ± 0.23 μA (n = 6). This decrease of current with cell shrinking was completely blocked by pretreatment of oocytes with cytochalasin B, indicating that these changes of current are not likely related to a direct effect of cell shrinking. We conclude that αβγ rENaC is not directly mechanosensitive when expressed in a system that can produce a channel with identical properties to those found in native epithelia.
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1 August 1998
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August 01 1998
Regulation of the Epithelial Na+ Channel by Membrane Tension
Mouhamed S. Awayda,
Mouhamed S. Awayda
From the *Department of Medicine, and ‡Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana 70112
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Muthangi Subramanyam
Muthangi Subramanyam
From the *Department of Medicine, and ‡Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana 70112
Search for other works by this author on:
Mouhamed S. Awayda
From the *Department of Medicine, and ‡Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana 70112
Muthangi Subramanyam
From the *Department of Medicine, and ‡Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana 70112
Address correspondence to Mouhamed S. Awayda, Department of Medicine, SL 35, Tulane University School of Medicine, New Orleans, LA 70112. Fax: 504-587-2188; E-mail: [email protected]
Received:
February 12 1998
Accepted:
March 25 1998
Online ISSN: 1540-7748
Print ISSN: 0022-1295
1998
J Gen Physiol (1998) 112 (2): 97–111.
Article history
Received:
February 12 1998
Accepted:
March 25 1998
Citation
Mouhamed S. Awayda, Muthangi Subramanyam; Regulation of the Epithelial Na+ Channel by Membrane Tension . J Gen Physiol 1 August 1998; 112 (2): 97–111. doi: https://doi.org/10.1085/jgp.112.2.97
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