title: Swelling-activated potassium channel in porcine pigmented ciliary epithelial cells.
abstract: OBJECTIVE
  Ion channels in the ciliary epithelium play critical roles in the formation of aqueous humor in the eye. The present study identified a novel, swelling-activated K(+) current in freshly dissociated porcine pigmented ciliary epithelial cells.
  
  
  METHODS
  Ciliary epithelial cells were freshly dissociated from porcine eyes. Whole-cell currents were recorded by the patch-clamp technique in pigmented and nonpigmented ciliary epithelial cell (PCE-NPCE) pairs or single PCE cells.
  
  
  RESULTS
  The 0-current potential was -49 ± 13 mV in PCE-NPCE cell pairs (n = 97) and -52 ± 12 mV in single PCE cells (n = 30). Whole-cell currents in these cells were dominated by an outwardly rectifying K(+) current activated by potentials more positive than -90 mV, which never inactivated during prolonged depolarization. The K(+) current was significantly augmented by hypotonic cell perfusion. External Ba(2+) was a blocker of this K(+) conductance (IC(50) of 0.38 mM), but the conductance was insensitive to external TEA(+). Linopirdine, a specific inhibitor of KCNQ channels, effectively blocked the K(+) current in these PCE cells.
  
  
  CONCLUSIONS
  Porcine PCE cells express a swelling-activated K(+) channel, which may be a member of the KCNQ/Kv7 channel family. This K(+) channel is active near resting potentials and could contribute to the regulation of cell volume and water transport via the ciliary epithelia.
authors.affiliation: Department of Ophthalmology and Visual Science, Kanazawa University, Kanazawa, Japan. takahira@kenroku.kanazawa-u.ac.jp
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takahira
authors.forename: Mayumi
authors.initials: M
authors.lastname: Sakurai
authors.forename: Norimasa
authors.initials: N
authors.lastname: Sakurada
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Sugiyama
mesh_terms: D000818:Animals; D048429:Cell Size; D002478:Cells, Cultured; D002924:Ciliary Body / Q000166:cytology / Q000502:physiology*; D004487:Edema / Q000473:pathology / Q000503:physiopathology*; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology*; D007038:Hypotonic Solutions / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D051656:KCNQ Potassium Channels / Q000502:physiology*; D008564:Membrane Potentials / Q000502:physiology; D008954:Models, Biological; D009997:Osmotic Pressure / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000502:physiology*; D034421:Sus scrofa; D019789:Tetraethylammonium / Q000494:pharmacology; D014867:Water / Q000378:metabolism
chemical_list: D007038:Hypotonic Solutions; D051656:KCNQ Potassium Channels; D026902:Potassium Channel Blockers; D014867:Water; D019789:Tetraethylammonium; D011188:Potassium