title: Fluid circulation determined in the isolated bovine lens.
abstract: OBJECTIVE
  In 1997, a theoretical model was developed that predicted the existence of an internal, Na(+)-driven fluid circulation from the poles to the equator of the lens. In the present work, we demonstrate with a novel system that fluid movement can be measured across the polar and equatorial surface areas of isolated cow lenses. We have also determined the effects of ouabain and reduced bath [Na(+)].
  
  
  METHODS
  Lenses were isolated in a chamber with three compartments separated by two thin O-rings. Each compartment, anterior (A), equatorial (E), and posterior (P), was connected to a vertical capillary graduated in 0.25 μL. Capillary levels were read every 15 minutes. The protocols consisted of 2 hours in either open circuit or short circuit. The effects of ouabain and low-Na(+) solutions were determined under open circuit.
  
  
  RESULTS
  In 21 experiments, the E capillary increased at a mean rate of 0.060 μL/min while the A and P levels decreased at rates of 0.044 and 0.037 μL/min, respectively, closely accounting for the increase in E. The first-hour flows under short circuit were approximately 40% larger than those in open-circuit conditions. The first-hour flows were always larger than those during the second hour. Preincubation of lenses with either ouabain or low-[Na(+)] solutions resulted in reduced rates of fluid transport. When KCl was used to replace NaCl, a transitory stimulation of fluid transport occurred.
  
  
  CONCLUSIONS
  These experiments support that a fluid circulation consistent with the 1997 model is physiologically active.
authors.affiliation: Department of Ophthalmology, Mount Sinai School of Medicine, New York, New York 10029, USA. oscar.candia@mssm.edu
authors.forename: Oscar A
authors.initials: OA
authors.lastname: Candia
authors.forename: Richard
authors.initials: R
authors.lastname: Mathias
authors.forename: Rosana
authors.initials: R
authors.lastname: Gerometta
mesh_terms: D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D002196:Capillaries / Q000502:physiology; D002199:Capillary Permeability / Q000187:drug effects; D002417:Cattle; D015194:Diffusion Chambers, Culture; D004581:Electronics / Q000379:methods; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004867:Equipment Design; D006874:Hydrostatic Pressure; D066298:In Vitro Techniques; D007908:Lens, Crystalline / Q000502:physiology*; D008954:Models, Biological; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000493:pharmacokinetics; D012964:Sodium / Q000493:pharmacokinetics; D012965:Sodium Chloride / Q000493:pharmacokinetics; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D012965:Sodium Chloride; D010042:Ouabain; D012964:Sodium; D011188:Potassium