HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 286/2/C380    most recent 00373.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (8) Citing Articles via Google Scholar Google Scholar Articles by Inagaki, A. Articles by Ishikawa, T. Search for Related Content PubMed PubMed Citation Articles by Inagaki, A. Articles by Ishikawa, T.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Amiloride-sensitive epithelial Na⁺ channel currents in surface cells of rat rectal colon

Laboratory of Physiology, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan

Submitted 2 September 2003 ; accepted in final form 14 October 2003

Surface cells of the mammalian distal colon are shown to molecularly express the amiloride-sensitive epithelial Na⁺ channel composed of three homologous subunits (-, -, and -ENaC). However, because basic electrophysiological properties of amiloride-sensitive Na⁺ channels expressed in these cells are largely unknown at the cellular level, functional evidence for the involvement of the subunits in the native channels is incomplete. Using electrophysiological techniques, we have now characterized functional properties of native ENaC in surface cells of rectal colon (RC) of rats fed a normal Na⁺ diet. Ussing chamber experiments showed that apical amiloride inhibited a basal short-circuit current in mucosal preparation of RC with an apparent half-inhibition constant (K_i) value of 0.20 µM. RT-PCR analysis confirmed the presence of transcripts of -, -, and -rENaC in rectal mucosa. Whole cell patch-clamp experiments in surface cells of intact crypts acutely isolated from rectal mucosa identified an inward cationic current, which was inhibited by amiloride with a K_i value of 0.12 µM at a membrane potential of –64 mV, the inhibition being weakly voltage dependent. Conductance ratios of the currents were Li⁺ (1.8) > Na⁺ (1) >> K⁺ (0), respectively. Amiloride-sensitive current amplitude was almost the same at 15 or 150 mM extracellular Na⁺, suggesting a high Na⁺ affinity for current activation. These results are consistent with the hypothesis that a heterooligomer composed of -, -, and -ENaC may be the molecular basis of the native channels, which are responsible for amiloride-sensitive electrogenic Na⁺ absorption in rat rectal colon.

distal colon; electrogenic Na⁺ absorption; short-circuit current; whole cell patch clamp; -ENaC

This article has been cited by other articles:

				M. Hatch and R. W. Freel Increased colonic sodium absorption in rats with chronic renal failure is partially mediated by AT1 receptor agonism Am J Physiol Gastrointest Liver Physiol, August 1, 2008; 295(2): G348 - G356. [Abstract] [Full Text] [PDF]

				M. T. Clunes, A. G. Butt, and S. M. Wilson A glucocorticoid-induced Na+ conductance in human airway epithelial cells identified by perforated patch recording J. Physiol., June 15, 2004; 557(3): 809 - 819. [Abstract] [Full Text] [PDF]