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N. Comes, T. Borras, M. Morales, A. Gual, X. Gasull; Identification and Electrophysiological Characterization of CLC–2 Chloride Channels in Trabecular Meshwork Cells: Modulation by pH and Cell Swelling . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1354.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Voltage–gated chloride channel ClC–2 participates in intracellular [Cl–] regulation, transepithelial transport and anionic homeostasis of cell–to–cell interactions. Moreover, it has been involved in cell volume regulation. Since changes in trabecular meshwork (TM) cells volume modify outflow facility, we studied the electrophysiological properties of an inwardly rectifying chloride current activated in human (HTM) and bovine trabecular meshwork (BTM) cells. To identify the possible molecular identity of the recorded currents we determined the expression of different CLCN genes in TM cells. Methods: Primary cultures of human and bovine TM cells were used. Inwardly rectifying chloride currents were characterized using the whole–cell configuration of the patch clamp technique. Total RNA was extracted from BTM and HTM cells and the expression of different CLCN genes was determined by RT–PCR using specific primers. Results of the PCR amplifications were sequenced to verify the identity of the CLCN transcripts in TM cells. Results: Patch–clamp recordings revealed inward rectifying chloride currents activated by membrane hyperpolarization. Electrophysiological properties and anion permeability sequence (Cl– > Br– > I– > Fl–) were in agreement with previous data for ClC–2 in other cells. Addition of Cd2+ significantly blocked this current. Cd2+–inhibited currents showed the typical inwardly rectification in both HTM and BTM cells. Extracellular alkalinization decreased ClC–2 currents while acidification or hypotonic cell swelling increased them. Finally, RT–PCR experiments revealed the molecular expression of ClC–2 as well as ClC–5, –6 and –7 in BTM cells, while ClC–1, –3 and –4 were not detected. ClC–2 to –7 channels were previously identified in HTM cells. Conclusions: Both human and bovine TM cells express functional ClC–2 channels that are modulated by changes in extracellular pH. Activation of ClC–2 channels after cell swelling and its participation in regulatory volume mechanisms will contribute to modulate outflow facility.
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