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R. Gerometta, O.A. Candia, L. Barrios; Effects of Bumetanide and Acetazolamide on the Cl–dependent Fluid Transport Across the Isolated Bovine Ciliary Epithelium . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3681.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To measure the effects of bumetanide and acetazolamide on the spontaneous fluid transport across the isolated bovine ciliary epithelium. Earlier studies examining the effects of acetazolamide on Cl and HCO3 fluxes across this tissue demonstrated that Cl is secreted with HCO3 providing a supporting role, as determined by the inhibitory effects of acetazolamide on net Cl fluxes and the absence of a net HCO3 flux. Methods: A complete annulus of ciliary body was mounted as a partition in a chamber designed for detecting net fluid movement. One side of the chamber had a 25 µl capillary allowing for detection of 0.25 µl changes in compartment volume. Either the aqueous (Aq) or blood (Bl) side interfaced with the capillary–containing compartment so that volume levels either increased or decreased coincident with the reversed mounting of the tissue. This was an indication that the flow was not an artifact. Results: A net fluid flow in the Bl–to–Aq direction of 2.92 ± 0.33 µl/hr · prep (n= 22) was measured. The baseline fluid transport rate lasted on average ≈ 4 hr. This flow solely reflects the secretory activity of the isolated ciliary epithelium in the absence of external osmotic or pressure gradients. In preparations exhibiting 40 min of spontaneous fluid transport, blood–side addition of bumetanide (10 µM), eliminated the flow within 10 min (n= 5). On the aqueous side, bumetanide eliminated fluid flow gradually in about 30 min (n= 4). Addition of 0.1 mM acetazolamide (n= 6 from each side) also led to a gradual decline in fluid transport that was complete in 40 min. In 7 preparations whereby SO4 was used to replace Cl on the blood side, fluid movement decreased from 3.68 ± 0.63 to –0.10 ± 0.64 µl/hr · prep; p < 0.01, as paired data, a change that was fully reversible on reintroduction of Cl. Overall, these data are consistent with earlier electrophysiological results. Conclusions: Bumetanide and acetazolaminde, which inhibited net Cl fluxes (Am J Physiol, 280: C1521, 2001), also inhibited the fluid secretion indicating its dependence on Cl transport.
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