December 2002
Volume 43, Issue 13
Free
ARVO Annual Meeting Abstract  |   December 2002
Regulation of Ion Transport Across Bovine Ciliary Body / Epithelium (CBE) by Cyclic AMP
Author Affiliations & Notes
  • CW Do
    Optometry & Radiography Hong Kong Polytechnic University Hong Kong Hong Kong Special Administrative Region of China
  • CH To
    Optometry & Radiography Hong Kong Polytechnic University Hong Kong Hong Kong Special Administrative Region of China
  • Footnotes
    Commercial Relationships   C.W. Do, None; C.H. To, None. Grant Identification: HKPU Research Grants GV423 and GT251
Investigative Ophthalmology & Visual Science December 2002, Vol.43, 3241. doi:
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      CW Do, CH To; Regulation of Ion Transport Across Bovine Ciliary Body / Epithelium (CBE) by Cyclic AMP . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3241.

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Abstract

Abstract: : Purpose: To investigate the role of cyclic AMP (cAMP) in the regulation of ion transport across the bovine CBE. Methods: Isolated bovine CBE preparation was dissected and mounted in a modified Ussing chamber. Electrical parameters including potential difference (PD), short-circuit current (Isc) and tissue resistance (Rt) were continuously monitored. Unidirectional Cl- fluxes were measured under short-circuited conditions. Results: The addition of cAMP-stimulating agents such as isoproterenol, VIP and forskolin all inhibited the Cl- secretion into the eye. Among these agents, forskolin was most effective in reducing the Cl- transport. Exogenous application of 8-Br-cAMP as well as IBMX also significantly reduced the Isc and Cl- secretion. These findings suggested a direct inhibitory effect of cAMP on ion transport across the ciliary epithelium. Pretreatment with NPPB at the blood side did not alter the baseline Isc and had no effect on the forskolin-induced Isc inhibition, suggesting that the reduction of Cl- transport was not due to the stimulation of Cl- absorption from aqueous humor to blood plasma. In contrast, pretreatment with heptanol at both sides blocked the forskolin-induced electrical responses, indicating that cAMP might reduce the ion transport by partially closing the gap junctions between PE and NPE cells. Conclusion: Our results suggested that cAMP regulated the ion transport across the ciliary epithelium. This effect might be mediated through the intercellular gap junctions between PE and NPE cells.

Keywords: 438 inflow/ciliary body • 577 second messengers: pharmacology/physiology • 416 gap junctions/coupling 
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