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Masayuki Takahira, Mayumi Sakurai, Norimasa Sakurada, Kazuhisa Sugiyama; Swelling-Activated Potassium Channel in Porcine Pigmented Ciliary Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2011;52(8):5928-5932. doi: https://doi.org/10.1167/iovs.11-7173.
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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.
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.
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 Ba2+ was a blocker of this K+ conductance (IC50 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.
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.
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