title: Experimental evidence of fluid secretion of rabbit lacrimal gland duct epithelium.
abstract: OBJECTIVE
  To investigate the osmotic water permeability of lacrimal gland (LG) duct epithelium by means of calculation of filtration permeability and to investigate LG ductal fluid secretion.
  
  
  METHODS
  Experiments were performed on isolated rabbit LG duct segments maintained in short-term culture. Osmotically determined fluid movement or fluid secretion into the closed intraluminal space of cultured LG interlobular ducts was analyzed using video microscopic technique.
  
  
  RESULTS
  The end of the LG ducts sealed after overnight incubation forming a closed luminal space. For the calculation of osmotic water permeability, ducts were initially perfused with isotonic HEPES buffered solution, and then with hypotonic HEPES buffered solution. Filtration permeability was calculated from the initial slope of the relative volume increase. Secretory responses to carbachol or to forskolin stimulation were also investigated. Forskolin stimulation resulted in a rapid and sustained secretory response in both solutions. Forskolin-stimulated fluid secretion was completely inhibited by bumetanide both in HEPES buffered and in HCO3 (-)/CO2 buffered solutions, suggesting the central role of Na(+)-K(+)-2Cl(-) cotransporter type 1 (NKCC1). Administration of carbachol initiated a rapid but short secretory response in both HEPES buffered and in HCO3 (-)/CO2 buffered solutions. Atropine completely abolished the carbachol-evoked fluid secretion.
  
  
  CONCLUSIONS
  A new method was introduced to investigate LG duct function. Water permeability of rabbit LG duct epithelium was measured by calculating filtration permeability. Fluid secretion of LG duct cells induced by carbachol or forskolin was also demonstrated. These results provide calculated values of lacrimal duct osmotic permeability and direct experimental evidence of LG duct fluid secretion.
authors.affiliation: 1st Department of Internal Medicine, University of Szeged, Szeged, Hungary Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.
authors.forename: Máté
authors.initials: M
authors.lastname: Katona
authors.affiliation: Department of Ophthalmology, University of Szeged, Szeged, Hungary.
authors.forename: Eszter
authors.initials: E
authors.lastname: Vizvári
authors.affiliation: Department of Medicinal Chemistry, University of Szeged, Szeged, Hungary.
authors.forename: Lukács
authors.initials: L
authors.lastname: Németh
authors.affiliation: Department of Ophthalmology, University of Szeged, Szeged, Hungary.
authors.forename: Andrea
authors.initials: A
authors.lastname: Facskó
authors.affiliation: Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary.
authors.forename: Viktória
authors.initials: V
authors.lastname: Venglovecz
authors.affiliation: 1st Department of Internal Medicine, University of Szeged, Szeged, Hungary.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Rakonczay
authors.affiliation: 1st Department of Internal Medicine, University of Szeged, Szeged, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Hegyi
authors.affiliation: Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary Department of Ophthalmology, University of Szeged, Szeged, Hungary.
authors.forename: Edit
authors.initials: E
authors.lastname: Tóth-Molnár
mesh_terms: D000818:Animals; D001285:Atropine / Q000494:pharmacology; D001692:Biological Transport; D001826:Body Fluids / Q000187:drug effects / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008297:Male; D018727:Muscarinic Antagonists / Q000494:pharmacology; D009301:Nasolacrimal Duct / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009994:Osmolar Concentration; D010539:Permeability / Q000187:drug effects; D011817:Rabbits; D046509:Tissue Culture Techniques; D014867:Water / Q000378:metabolism
chemical_list: D018679:Cholinergic Agonists; D018727:Muscarinic Antagonists; D014867:Water; D001285:Atropine; D002217:Carbachol
keywords: epithelial cells; fluid secretion; lacrimal gland; lacrimal gland duct