Identification and functional characterization of ClC-2 chloride channels in trabecular meshwork cells.
In the eye, trabecular meshwork (TM) cell volume may be an important determinant of aqueous humor outflow. Among their functions, ClC-2 chloride channels are thought to be involved in regulation of cellular volume and intracellular [Cl(-)]. We characterized the properties and modulation of an inwardly rectifying chloride current activated in these cells. Patch-clamp recordings revealed inwardly rectifying chloride currents activated by membrane hyperpolarization in primary cultures of both bovine (BTM) and human (HTM) TM cells. Electrophysiological properties and anion permeability sequence (Cl(-)>Br(-)>I(-)>F(-)) were in agreement with previous data for ClC-2 in other cells. The currents were blocked by Cd(2+) and enhanced by extracellular acidification, 8Br-cAMP and cell swelling, while extracellular alkalinization decreased them. RT-PCR experiments using total RNA revealed the molecular expression of ClC-2 channels. Previously we reported the involvement of swelling-activated chloride channels (Cl(swell)) and Ca(2+)-activated K(+) channels (BK(Ca)) in cell volume and outflow facility regulation. However, in the present analysis, cell volume experiments in calcein-loaded cells and outflow facility studies performed in bovine anterior segments revealed that ClC-2 channels do not make a significant contribution to the recovery of cellular volume or to the regulation of the outflow facility. Nevertheless, ClC-2 modulation by different stimuli may contribute to intracellular [Cl(-)] regulation and other cellular functions yet to be determined in the TM.
Comes
Núria
N
Laboratory of Neurophysiology, Department of Physiological Sciences I-Institute of Biomedical Investigations August Pi i Sunyer, IDIBAPS, School of Medicine, University of Barcelona, Casanova 143, E-08036 Barcelona, Spain.
Abad
Elena
E
Morales
Miguel
M
Borrás
Teresa
T
Gual
Arcadi
A
Gasull
Xavier
X
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D000090007:CLC-2 Chloride Channels; D002104:Cadmium / Q000494:pharmacology; D002417:Cattle; D048429:Cell Size; D002478:Cells, Cultured; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D018408:Patch-Clamp Techniques / Q000379:methods; D014129:Trabecular Meshwork / Q000166:cytology / Q000378:metabolism* / Q000502:physiology
D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels; D002104:Cadmium; D015124:8-Bromo Cyclic Adenosine Monophosphate