Na+-K+-Cl- cotransporter (NKCC) maintains the chloride gradient to sustain pacemaker activity in interstitial cells of Cajal

Mei Hong Zhu; Tae Sik Sung; Masaaki Kurahashi; Lauren E O'Kane; Kate O'Driscoll; Sang Don Koh; Kenton M Sanders

doi:10.1152/ajpgi.00277.2016

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Na+-K+-Cl- cotransporter (NKCC) maintains the chloride gradient to sustain pacemaker activity in interstitial cells of Cajal

Journal article

Open access

Peer reviewed

Na+-K+-Cl- cotransporter (NKCC) maintains the chloride gradient to sustain pacemaker activity in interstitial cells of Cajal

Mei Hong Zhu, Tae Sik Sung, Masaaki Kurahashi, Lauren E O'Kane, Kate O'Driscoll, Sang Don Koh and Kenton M Sanders

American journal of physiology: Gastrointestinal and liver physiology, Vol.311(6), pp.G1037-G1046

12/01/2016

DOI: 10.1152/ajpgi.00277.2016

PMCID: PMC5206290

PMID: 27742704

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Abstract

Interstitial cells of Cajal (ICC) generate electrical slow waves by coordinated openings of ANO1 channels, a Ca -activated Cl (CaCC) conductance. Efflux of Cl during slow waves must be significant, as there is high current density during slow-wave currents and slow waves are of sufficient magnitude to depolarize the syncytium of smooth muscle cells and PDGFRα cells to which they are electrically coupled. We investigated how the driving force for Cl current is maintained in ICC. We found robust expression of Slc12a2 (which encodes an Na -K -Cl cotransporter, NKCC1) and immunohistochemical confirmation that NKCC1 is expressed in ICC. With the use of the gramicidin permeabilized-patch technique, which is reported to not disturb [Cl ] , the reversal potential for spontaneous transient inward currents (E ) was -10.5 mV. This value corresponds to the peak of slow waves when they are recorded directly from ICC in situ. Inhibition of NKCC1 with bumetanide shifted E to more negative potentials within a few minutes and reduced pacemaker activity. Bumetanide had no direct effects on ANO1 or Ca 3.2 channels expressed in HEK293 cells or L-type Ca currents. Reducing extracellular Cl to 10 mM shifted E to positive potentials as predicted by the Nernst equation. The relatively rapid shift in E when NKCC1 was blocked suggests that significant changes in the transmembrane Cl gradient occur during the slow-wave cycle, possibly within microdomains formed between endoplasmic reticulum and the plasma membrane in ICC. Recovery of Cl via NKCC1 might have additional consequences on shaping the waveforms of slow waves via Na entry into microdomains.

Action Potentials

Animals

Bumetanide - pharmacology

Calcium Channels, T-Type - metabolism

Cells, Cultured

Chlorides - metabolism

HEK293 Cells

Humans

Interstitial Cells of Cajal - drug effects

Interstitial Cells of Cajal - metabolism

Interstitial Cells of Cajal - physiology

Mice

Periodicity

Sodium Potassium Chloride Symporter Inhibitors - pharmacology

Solute Carrier Family 12, Member 2 - genetics

Solute Carrier Family 12, Member 2 - metabolism

Details

Title: Subtitle: Na+-K+-Cl- cotransporter (NKCC) maintains the chloride gradient to sustain pacemaker activity in interstitial cells of Cajal
Creators: Mei Hong Zhu - University of Nevada Reno
Tae Sik Sung - University of Nevada Reno
Masaaki Kurahashi - University of Nevada Reno
Lauren E O'Kane - University of Nevada Reno
Kate O'Driscoll - University of Nevada Reno
Sang Don Koh - University of Nevada Reno
Kenton M Sanders - University of Nevada Reno
Resource Type: Journal article
Publication Details: American journal of physiology: Gastrointestinal and liver physiology, Vol.311(6), pp.G1037-G1046
DOI: 10.1152/ajpgi.00277.2016
PMID: 27742704
PMCID: PMC5206290
ISSN: 0193-1857
eISSN: 1522-1547
Grant note: P01 DK041315 / NIDDK NIH HHS R01 DK091336 / NIDDK NIH HHS
Language: English
Date published: 12/01/2016
Academic Unit: Internal Medicine
Record Identifier: 9984359672202771

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