title: Blocking chloride channels in the rat lens: localized changes in tissue hydration support the existence of a circulating chloride flux.
abstract: OBJECTIVE
  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 microM 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 microM, (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 regulator p-glycoprotein.
  
  
  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.
authors.affiliation: Department of Physiology, Faculty of Medicine and Health Science. School of Biological Sciences, University of Auckland, New Zealand.
authors.forename: M A
authors.initials: MA
authors.lastname: Young
authors.forename: M J
authors.initials: MJ
authors.lastname: Tunstall
authors.forename: J
authors.initials: J
authors.lastname: Kistler
authors.forename: P J
authors.initials: PJ
authors.lastname: Donaldson
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000494:pharmacology; D000818:Animals; D001834:Body Water / Q000378:metabolism*; D018118:Chloride Channels / Q000037:antagonists & inhibitors*; D002712:Chlorides / Q000378:metabolism*; D007908:Lens, Crystalline / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure*; D018613:Microscopy, Confocal; D009579:Nitrobenzoates / Q000494:pharmacology*; D009924:Organ Culture Techniques; D009929:Organ Size; D051381:Rats; D017208:Rats, Wistar; D013629:Tamoxifen / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D002712:Chlorides; D009579:Nitrobenzoates; D013629:Tamoxifen; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid