title: Applicability of the Ussing chamber technique to permeability determinations in functionally distinct regions of the gastrointestinal tract in the rat.
abstract: BACKGROUND
  Ussing chambers are commonly utilized for in vitro investigations into gastrointestinal permeability. However, their sensitivity and applicability to the small intestine have not been well characterized.
  
  
  METHODS
  In order to investigate the effects of experimentally induced damage and the relative contribution of the mucosa and muscularis externa layers to transmural permeability in the small intestine, stomach and colon, normal rat intestinal tissues were mounted in Ussing chambers with or without removal of the muscularis externa or mucosal layers. Gastric tissues were damaged in vivo by exposure to indomethacin (100 mg kg(-1)), while ileal tissues were damaged in vitro by 0.4 M NaCl. Tissue damage was assessed histologically, while permeability parameters included conductance (G), potential difference (PD) and mucosal to serosal flux of horseradish peroxidase (HRP).
  
  
  RESULTS
  Damage localized to the tissue edges (edge damage) accounted for 25%-50% of the exposed epithelial length in the ileum, while less than 20% of stomach and colon epithelium was affected by edge damage. In the damaged stomach, a 20% reduction in epithelialization was accompanied by increases in G (P < 0.001) and HRP (P < 0.01) flux. Removal of the muscularis externa did not affect mucosal viability in the undamaged ileum or colon although HRP flux in the colon, but not ileum, was increased (P < 0.01). Removal of the ileal mucosa produced increases in G and HRP flux, while PD was maintained.
  
  
  CONCLUSIONS
  We conclude that the Ussing chamber technique is suitable for application to studies of gastric and colonic permeability in rats. However, owing to the prevalence and extent of edge damage in the small intestine, we would caution against the use of this technique for permeability studies in this region of the gastrointestinal tract in the rat.
authors.affiliation: Child Health Research Institute and Cooperative Research Centre for Tissue Growth and Repair, Adelaide, South Australia, Australia.
authors.forename: B H
authors.initials: BH
authors.lastname: Bajka
authors.forename: C M
authors.initials: CM
authors.lastname: Gillespie
authors.forename: C B
authors.initials: CB
authors.lastname: Steeb
authors.forename: L C
authors.initials: LC
authors.lastname: Read
authors.forename: G S
authors.initials: GS
authors.lastname: Howarth
mesh_terms: D000818:Animals; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D015194:Diffusion Chambers, Culture; D004195:Disease Models, Animal; D005753:Gastric Mucosa / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects; D008297:Male; D010539:Permeability; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012965:Sodium Chloride / Q000494:pharmacology; D013270:Stomach / Q000187:drug effects
chemical_list: D012965:Sodium Chloride; D007213:Indomethacin