The influence of hypotonicity on large-conductance calcium-activated potassium channels in human retinal pigment epithelial cells

Shwu Jiuan Sheu, Sheng Nan Wu, Dan Ning Hu, Jane Fane Chen

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The aim of this study was to characterize the effects of hypotonicity on the activity of large-conductance Ca2+-activated K+ (BKCa) channels in human retinal pigment epithelial (RPE R-50) cells. Effects of hypotonicity on ion currents were investigated with the aid of the patch-clamp technique. A regulatory volume decrease in response to a hypotonic solution (200 mOsm/L) was observed that could be blunted by paxilline. In whole-cell current recordings, a hypotonic solution (200 mOsm/L) reversibly increased the amplitude of K+ outward currents (IK). The increase of IK could be reversed by iberiotoxin (200 nM), paxilline (1 μM), or tetrandrine (5 μM), but not by glibenclamide (10 μM), disulphonic acid (DIDS) (100 μM), or dequalinium dichloride (10 μM). In RPE R-50 cells pretreated with thapsigargin, aristolochic acid, or pertussis toxin, the increased amplitude of IK in response to hypotonicity was unaltered. In cell-attached patches, an increase in BKCa-channel activity was observed during hypotonicity-induced cell swelling. The enhanced channel activity elicited under this condition was mainly mediated by an increase in the number of long-lived openings. These findings support the evidence for the coupling of volume swelling to the functional activity of BKCa channels.

Original languageEnglish
Pages (from-to)563-575
Number of pages13
JournalJournal of Ocular Pharmacology and Therapeutics
Volume20
Issue number6
DOIs
Publication statusPublished - 2004 Dec 1

All Science Journal Classification (ASJC) codes

  • Ophthalmology
  • Pharmacology
  • Pharmacology (medical)

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