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Ca 2+ sensitivity of the maxi chloride channel in interstitial cells of Cajal
Author(s) -
Wright G. W. J.,
Parsons S. P.,
Huizinga J. D.
Publication year - 2012
Publication title -
neurogastroenterology and motility
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.489
H-Index - 105
eISSN - 1365-2982
pISSN - 1350-1925
DOI - 10.1111/j.1365-2982.2012.01881.x
Subject(s) - chloride channel , biophysics , interstitial cell of cajal , intracellular , patch clamp , chemistry , membrane potential , electrophysiology , chloride , anatomy , biochemistry , biology , endocrinology , neuroscience , smooth muscle , receptor , organic chemistry
Background Interstitial cells of Cajal (ICC) associated with the myenteric plexus of the small intestine express maxi chloride channels. Our aim was to investigate whether or not these channels would be activated by increases in intracellular Ca 2+ , as that would strengthen evidence for their potential role in ICC pacemaking. A further aim was to examine whether inwardly and outwardly rectifying maxi chloride currents signify different channels. Methods We used Fluo‐4 AM Ca 2+ imaging and patch clamp electrophysiology (cell‐attached and inside‐out) on isolated ICC in short term culture. Key Results Increasing intracellular Ca 2+ by three functionally distinct mechanisms (blocking sarcoplasmic reticulum Ca 2+ refilling, creating membrane Ca 2+ pores and a solution designed to block plasmalemmal Ca 2+ extrusion) was followed by inwardly rectifying maxi chloride channel activation assessed in the cell‐attached configuration. Furthermore, in the inside‐out configuration, increased outwardly rectifying maxi‐chloride channel activity followed an increase in Ca 2+ to 2 mmol L −1 at the cytoplasmic face of the channel. Conclusions & Inferences Increase in intracellular Ca 2+ will activate the maxi chloride channels. Maxi chloride currents are inwardly rectifying in the cell‐attached patch clamp configuration under physiological conditions and are outwardly rectifying in the inside‐out configuration. The same channel is responsible for both currents. Ca 2+ does not appear to regulate the rectification.