May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
Potential Role of Pannexin Hemichannels in ATP Release From Native Bovine Ciliary Epithelial Cells
Author Affiliations & Notes
  • A. Li
    University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania
    Department of Physiology,
  • W. Lu
    University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania
    Department of Physiology,
  • G. C. T. Leung
    University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania
    Department of Physiology,
  • K. Peterson-Yantorno
    University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania
    Department of Physiology,
  • C. H. Mitchell
    University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania
    Department of Physiology,
  • M. M. Civan
    University of Pennsylvania, School of Medicine, Philadelphia, Pennsylvania
    Department of Physiology,
    Department of Medicine,
  • Footnotes
    Commercial Relationships  A. Li, None; W. Lu, None; G.C.T. Leung, None; K. Peterson-Yantorno, None; C.H. Mitchell, None; M.M. Civan, None.
  • Footnotes
    Support  NIH Research Grants EY13624 (M.M.C.) and EY 015537 (C.H.M.) and Core Grant EY01583
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 3161. doi:https://doi.org/
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    • Get Citation

      A. Li, W. Lu, G. C. T. Leung, K. Peterson-Yantorno, C. H. Mitchell, M. M. Civan; Potential Role of Pannexin Hemichannels in ATP Release From Native Bovine Ciliary Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3161. doi: https://doi.org/.

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

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Abstract

Purpose: : To determine whether the recently-identified, ubiquitous pannexin hemichannels serve as a conduit for ATP release, the first step in purinergic signaling and regulation of aqueous humor dynamics.

Methods: : Mixed populations of non-pigmented (NPE) and pigmented (PE) ciliary epithelial cells were harvested from bovine ciliary processes. Cell ATP release was measured with a luminometer by the luciferin-luciferase reaction 24-48 hrs after plating into 96-well microplates. Cells were preincubated isotonically with/without drugs for 1 hr, and stimulated by 50% hypotonicity. ATP concentrations were calibrated in isotonic standard solutions and in hypotonic standard solutions with/without carbenoxolone (CBX), flufenamic acid (FFA) or NPPB.

Results: : ATP release by fresh bovine NPE and PE cells was readily measured. ATP concentration in the bath was 2.4 +0.1 nM (mean ±SE, n=124 wells) in control isotonic solution, increasing 3-fold to 8.6 +0.5 nM (n=114, P<0.001) after hypotonic exposure. CBX reduced hypotonicity-induced ATP release by 32 +6%, 45 +6%, and 52 +5% at 1 µM, 3 µM and 30 µM, respectively. The potency of CBX was very high, with a calculated IC50 of 0.7 +0.1 µM (n=15). FFA reduced the ATP release at 30 µM by 60 +4% (n=32). NPPB inhibited hypotonically-elicited release by 59 ±3% (n=57) at 100 µM, without affecting isotonic ATP release (n=30, P=0.469).

Conclusions: : CBX reduced hypotonically-triggered ATP release of native NPE and PE cells with high potency, a signature characteristic of pannexin hemichannels. However, the maximum inhibition by CBX was only ~50%, raising the possibility of at least 2 conduits for ATP release. Since ATP release is the first step in purinergic regulation of aqueous dynamics, the current data suggest the possibility of a novel approach in selectively blocking ATP conduits in order to lower intraocular pressure.

Keywords: ion channels • gap junctions/coupling • adenosine 
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