May 2004
Volume 45, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2004
Regulation of Cl– reabsorption by pigmented ciliary epithelial cells: Effects of ATP and cytoplasmic Cl– concentration
Author Affiliations & Notes
  • M.M. Civan
    Department of Physiology, Univ of Pennsylvania, Philadelphia, PA
  • C.W. Do
    Department of Physiology, Univ of Pennsylvania, Philadelphia, PA
  • C.H. Mitchell
    Department of Physiology, Univ of Pennsylvania, Philadelphia, PA
  • Footnotes
    Commercial Relationships  M.M. Civan, None; C.W. Do, None; C.H. Mitchell, None.
  • Footnotes
    Support  NIH Research Grant EY 08343 and EY 13434 and Core Grant EY 01583
Investigative Ophthalmology & Visual Science May 2004, Vol.45, 419. doi:
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      M.M. Civan, C.W. Do, C.H. Mitchell; Regulation of Cl– reabsorption by pigmented ciliary epithelial cells: Effects of ATP and cytoplasmic Cl– concentration . Invest. Ophthalmol. Vis. Sci. 2004;45(13):419.

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

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Abstract

Abstract: : Purpose:We have previously demonstrated that cAMP stimulates whole–cell Cl currents and activates maxi–Cl channels in native bovine pigmented ciliary epithelial (PE) cells. In the present study, we examined the physiological relevance in regulating the Cl reabsorption. Methods:Whole–cell configuration, excised inside–out and outside–out patches were performed in native bovine PE cells. Results:At 30mM cytoplasmic Cl, 8–Br–cAMP stimulated whole–cell Cl currents by ∼25%. Under constant bath Cl concentration of 140mM, increasing cytoplasmic Clconcentration to 140mM doubled the cAMP–activated currents. ATP (10–100µM) stimulated the whole–cell currents by ∼10%, but did not enhance the cAMP–activated currents. Like inside–out patches, addition of 8–Br–cAMP to the bath activated maxi–Cl channels in outside–out patches of native bovine PE cells. At symmetrical 130mM NaCl solutions, the channels displayed a conductance of ∼270pS. In agreement with the results of whole–cell measurements, decreasing the cytoplasmic Cl concentration in excised inside–out patches caused a significant inhibition of maxi–Cl channel currents, reflecting a reduction of both channel open probability (Po) and unitary conductance. Conclusions:The absence of synergistic effects of ATP and cAMP in stimulating the whole–cell currents suggested that ATP and cAMP might share the common sequential cascade to trigger the Cl channel activation. Cytoplasmic Cl concentration exerted significant effects in modulating cAMP–activated Cl channels. Increasing cytoplasmic Cl concentration enhanced both whole–cell currents and maxi–Cl channel currents activated by cAMP by increasing both Po and the unitary conductance. Our results suggest that cAMP facilitates Cl recycling in PE cells, particularly in cells loaded with high intracellular Cl concentration, thereby potentially reducing net Cl secretion. This pathway may be of physiologic importance in regulating net aqueous humor formation and thereby intraocular pressure.

Keywords: inflow/ciliary body • ion channels • second messengers: pharmacology/physiology 
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