title: Maxi-channels recorded in situ from ICC and pericytes associated with the mouse myenteric plexus.
abstract: Ion channels are fundamental to gastrointestinal pacemaking by interstitial cells of Cajal (ICC). Previously, we have recorded a high-conductance chloride channel (HCCC) from ICC, both in culture and in situ, associated with the myenteric plexus. The biophysical properties of the HCCC (conductance, subconductances, voltage- and time-dependent inactivation) suggest it is a member of a class called the maxi-anion channels. In this study we further investigated the properties of the HCCC in situ. Our main finding was that the HCCC is not strictly a chloride channel but has a relative sodium-chloride permeability (P(Na/Cl)) of 0.76 to 1.64 (depending on the method of measurement). Therefore, we have renamed the HCCC the "maxi-channel." A maxi-channel was also expressed by pericytes associated with the vasculature near the myenteric plexus. This had a lower P(Na/Cl) (0.33 to 0.49, depending on the method of measurement) but similar conductance (326 ± 7 vs. 316 ± 24 pS for ICC). This is the first report of cation permeability equaling anion permeability in a maxi-anion channel. As such, the properties of the maxi-channels described in this article may have implications for the maxi-anion channel field, as well as for studies of their role in ICC and pericytes.
authors.affiliation: Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, ON, Canada.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Parsons
authors.forename: Wolfgang A
authors.initials: WA
authors.lastname: Kunze
authors.forename: Jan D
authors.initials: JD
authors.lastname: Huizinga
mesh_terms: D000818:Animals; D000838:Anions / Q000378:metabolism; D002463:Cell Membrane Permeability; D018118:Chloride Channels / Q000378:metabolism / Q000502:physiology*; D004553:Electric Conductivity; D056885:Interstitial Cells of Cajal / Q000378:metabolism / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D009197:Myenteric Plexus / Q000378:metabolism / Q000502:physiology*; D020286:Pericytes / Q000378:metabolism / Q000502:physiology*; D012964:Sodium / Q000378:metabolism; D013368:Submucous Plexus / Q000378:metabolism / Q000502:physiology
chemical_list: D000838:Anions; D018118:Chloride Channels; D012964:Sodium