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Miriam A. Young, Mark J. Tunstall, Joerg Kistler, Paul J. Donaldson; Blocking Chloride Channels in the Rat Lens: Localized Changes in Tissue Hydration Support the Existence of a Circulating Chloride Flux. Invest. Ophthalmol. Vis. Sci. 2000;41(10):3049-3055.
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purpose. To investigate the effects of inhibitors of chloride channels on lens
volume and tissue architecture under isotonic conditions.
methods. Rat lenses were maintained in organ culture under isotonic conditions
in the presence of various putative chloride channel inhibitors. The
effect of an inhibitor on lens wet mass and tissue morphology was
determined by weighing and histologic examination, respectively.
results. Exposure to 100 μM of either 5-nitro-2- (3-phenylpropylamino) benzoic
acid (NPPB) or 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid
(DIDS) caused an increase in wet mass and severe tissue disruption in
the lens equatorial region. Two distinctly different zones of tissue
damage were evident: a peripheral zone of fiber cell swelling and an
inner zone of extensive tissue breakdown. Extracellular space dilations
caused the extensive tissue damage in the inner zone and preceded the
peripheral fiber cell swellings. That the observed effects were a
consequence of the inhibition of chloride channels was supported by (1)
the effectiveness of NPPB at the lower dose of 10 μM, (2) the absence
of any NPPB effect in chloride-free medium, and (3) an identical effect
after exposure to tamoxifen, an inhibitor of the chloride channel
conclusions. Study results indicate that chloride channels are active in the lens
under isotonic conditions. The spatial and temporal pattern of
morphologic changes that was observed is consistent with a steady state
efflux of chloride ions and water from peripheral fiber cells and a
corresponding influx into fiber cells deeper in the lens. These
observations may therefore represent the first visualization of the
chloride flux postulated by others to be a component of the lens
internal circulation system.
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