Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/17954
Title: Model of ionic transport for bovine ciliary epithelium : effects of acetazolamide and HCO3 -
Authors: To, CH 
Do, CW
Zamudio, AC
Candia, OA
Keywords: Aqueous humor secretion
Bicarbonate fluxes
Chloride fluxes
Short-circuit current
Ussing chamber
Issue Date: 2001
Publisher: American Physiological Society
Source: American journal of physiology. Cell physiology, 2001, v. 280, no. 6 49-6, p. c1521-c1530 How to cite?
Journal: American journal of physiology. Cell physiology 
Abstract: The possible existence of transepithelial bicarbonate transport across the isolated bovine ciliary body was investigated by employing a chamber that allows for the measurement of unidirectional, radio-labeled fluxes of CO2 + HCO3 -. No net flux of HCO3 - was detected. However, acetazolamide (0.1 mM) reduced the simultaneously measured short-circuit current (Isc). In other experiments in which 36Cl- was used, a net Cl- flux of 1.12 μeq·h-1·cm-2 (30 μA/cm2) in the blood-to-aqueous direction was detected. Acetazolamide, as well as removal of HCO3 - from the aqueous bathing solution, inhibited the net Cl- flux and Isc. Because such removal should increase HCO3 - diffusion toward the aqueous compartment and increase the Isc, this paradoxical effect could result from cell acidification and partial closure of Cl- channels. The acetazolamide effect on Cl- fluxes can be explained by a reduction of cellular H+ and HCO3 - (generated from metabolic CO2 production), which exchange with Na+ and Cl- via Na+/H+ and Cl-/HCO3 - exchangers, contributing to the net Cl- transport. The fact that the net Cl- flux is about three times larger than the Isc is explained with a vectorial model in which there is a secretion of Na+ and K+ into the aqueous humor that partially subtracts from the net Cl- flux. These transport characteristics of the bovine ciliary epithelium suggest how acetazolamide reduces intraocular pressure in the absence of HCO3 - transport as a driving force for fluid secretion.
URI: http://hdl.handle.net/10397/17954
ISSN: 0363-6143
EISSN: 1522-1563
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