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Potassium currents in cultured rabbit retinal pigment epithelial cells

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Abstract

Membrane potential and ionic currents were studied in cultured rabbit retinal pigment epithelial (RPE) cells using whole-cell patch clamp and perforated-patch recording techniques. RPE cells exhibited both outward and inward voltage-dependent currents and had a mean membrane capacitance of 26±12 pF (sd, n=92). The resting membrane potential averaged −31±15 mV (n=37), but it was as high as −60 mV in some cells. When K+ was the principal cation in the recording electrode, depolarization-activated outward currents were apparent in 91% of cells studied. Tail current analysis revealed that the outward currents were primarily K+ selective. The most frequently observed outward K+ current was a voltage- and time-dependent outward current (I K) which resembled the delayed rectifier K+ current described in other cells. I K was blocked by tetraethylammonium ions (TEA) and barium (Ba2+) and reduced by 4-aminopyridine (4-AP). In a few cells (3–4%), depolarization to −50 mV or more negative potentials evoked an outwardly rectifying K+ current (I Kt) which showed more rapid inactivation at depolarized potentials. Inwardly rectifying K+ current (I KI) was also present in 41% of cells. I KI was blocked by extracellular Ba2+ or Cs+ and exhibited time-dependent decay, due to Na+ blockade, at negative potentials. We conclude that cultured rabbit RPE cells exhibit at least three voltage-dependent K+ currents. The K+ conductances reported here may provide conductive pathways important in maintaining ion and fluid homeostasis in the subretinal space.

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Authors and Affiliations

  1. Department of Pharmacology, Tupper Medical Building, Dalhousie University, B3H 4H7, Halifax, Nova Scotia, Canada

    Q. Tao & M. E. M. Kelly

  2. Department of Ophthalmology, Dalhousie University, Halifax, Nova Scotia, Canada

    P. E. Rafuse

Authors
  1. Q. Tao
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  2. P. E. Rafuse
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  3. M. E. M. Kelly
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Additional information

We wish to thank Jonathan Blay for his advice on matters related to cell culture, John Poyer and Susan Howlett for their comments on the manuscript and Christine Jollimore for her expert technical support. This work was funded by Natural Sciences and Engineering Research Council of Canada grant OGP0121657 and the Retinitis Pigmentosa Research Foundation. Q-P.T. is funded by an Retinitis Pigmentosa Research Foundation Studentship award.

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Tao, Q., Rafuse, P.E. & Kelly, M.E.M. Potassium currents in cultured rabbit retinal pigment epithelial cells. J. Membarin Biol. 141, 123–138 (1994). https://doi.org/10.1007/BF00238246

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  • DOI: https://doi.org/10.1007/BF00238246

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