title: Uroguanylin is expressed by enterochromaffin cells in the rat gastrointestinal tract.
abstract: OBJECTIVE
  Guanylin and uroguanylin are recently discovered intestinal peptides. Identifying the type of cell that synthesizes and secretes each peptide is an important step toward defining their physiological functions. However, the site of uroguanylin expression has not been identified, and the site of guanylin expression remains controversial (some studies implicate goblet cells, whereas others implicate enterochromaffin cells). The aim of the present study was to identify cellular sites of uroguanylin expression in the rat gastrointestinal tract and resolve the guanylin localization controversy.
  
  
  METHODS
  Polyclonal antibodies against two independent regions of the uroguanylin prohormone were raised and used to evaluate prouroguanylin expression by Western blotting and immunohistochemistry. In parallel, uroguanylin mRNA was localized by in situ hybridization.
  
  
  RESULTS
  Uroguanylin propeptide expression is high in proximal small intestine, low in stomach and distal small intestine, and almost undetectable in large intestine. Uroguanylin-expressing cells are identified as a subpopulation of enterochromaffin cells.
  
  
  CONCLUSIONS
  Previous results showing guanylin expression in enterochromaffin cells appear to be a consequence of antibody cross-reactivity for epitopes conserved between proguanylin and prouroguanylin. Expression of uroguanylin in enterochromaffin cells is consistent with the hypothesis that uroguanylin is secreted both apically (into the lumen) and basolaterally (into the circulation).
authors.affiliation: Department of Physiology, University of North Carolina, Chapel Hill, USA.
authors.forename: A
authors.initials: A
authors.lastname: Perkins
authors.forename: M F
authors.initials: MF
authors.lastname: Goy
authors.forename: Z
authors.initials: Z
authors.lastname: Li
mesh_terms: D000818:Animals; D004064:Digestive System / Q000166:cytology / Q000378:metabolism*; D004759:Enterochromaffin Cells / Q000378:metabolism*; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D045265:Natriuretic Peptides; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
chemical_list: D045265:Natriuretic Peptides; D010455:Peptides; D011498:Protein Precursors; D012333:RNA, Messenger; C097400:prouroguanylin; C084362:uroguanylin