May 1996
Volume 37, Issue 6
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Articles  |   May 1996
Inwardly rectifying K+ currents in isolated human retinal pigment epithelial cells.
Author Affiliations
  • B A Hughes
    Department of Opthalmology, University of Michigan, Ann Arbor 48105, USA.
  • M Takahira
    Department of Opthalmology, University of Michigan, Ann Arbor 48105, USA.
Investigative Ophthalmology & Visual Science May 1996, Vol.37, 1125-1139. doi:
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    • Get Citation

      B A Hughes, M Takahira; Inwardly rectifying K+ currents in isolated human retinal pigment epithelial cells.. Invest. Ophthalmol. Vis. Sci. 1996;37(6):1125-1139.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

PURPOSE: K+ channels in the retinal pigment epithelium (RPE) play a number of important roles, including the establishment of membrane potential, the transport of K+ between the subretinal space and choroid, and the generation of the c-wave of the electroretinogram. Previous studies on amphibian RPE demonstrated that these functions are likely served by an inwardly rectifying K+ channel. The aim of this study was to characterize inwardly rectifying K+ channels in cultured and freshly isolated adult human RPE (hRPE) cells. METHODS: Single cells were dispersed enzymatically from primary cultures of adult hRPE or from fresh adult hRPE-choroid. Ionic currents were recorded using either the perforated-patch or whole-cell configuration of the patch-clamp technique. RESULTS: In 5 mM external K+, roughly 20% of cultured hRPE cells exhibited a strong inwardly rectifying K+ conductance that passed inward but little outward current. This conductance increased when [K+]o was increased and exhibited a voltage-dependent block by external Na+ at negative potentials. In contrast, all freshly isolated hRPE cells exhibited a mild inwardly rectifying K+ conductance that mediated substantial outward current at physiological voltages. This conductance decreased when [K+]o was increased and showed no voltage-dependent block by external Na+. CONCLUSION: The authors conclude that fresh hRPE cells express a mild inwardly rectifying K+ conductance. The operation of this conductance at physiological voltages makes it a likely candidate for the resting K+ conductances of the apical and basolateral membranes. Cultured hRPE cells express a functionally different channel type that may reflect a change in phenotype.

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