title: GLP-1 and GIP are colocalized in a subset of endocrine cells in the small intestine.
abstract: BACKGROUND
  The incretin hormones GIP and GLP-1 are thought to be produced in separate endocrine cells located in the proximal and distal ends of the mammalian small intestine, respectively.
  
  
  RESULTS
  Using double immunohistochemistry and in situ hybridization, we found that GLP-1 was colocalized with either GIP or PYY in endocrine cells of the porcine, rat, and human small intestines, whereas GIP and PYY were rarely colocalized. Thus, of all the cells staining positively for either GLP-1, GIP, or both, 55-75% were GLP-1 and GIP double-stained in the mid-small intestine. Concentrations of extractable GIP and PYY were highest in the midjejunum [154 (95-167) and 141 (67-158) pmol/g, median and range, respectively], whereas GLP-1 concentrations were highest in the ileum [92 (80-207) pmol/l], but GLP-1, GIP, and PYY immunoreactive cells were found throughout the porcine small intestine.
  
  
  CONCLUSIONS
  Our results provide a morphological basis to suggest simultaneous, rather than sequential, secretion of these hormones by postprandial luminal stimulation.
authors.affiliation: Department of Medical Anatomy, The Panum Institute, University of Copenhagen, Blegdamsvej 3 C, Copenhagen DK-2200, Denmark.
authors.forename: Kristine
authors.initials: K
authors.lastname: Mortensen
authors.forename: Louise Lundby
authors.initials: LL
authors.lastname: Christensen
authors.forename: Jens Juul
authors.initials: JJ
authors.lastname: Holst
authors.forename: Cathrine
authors.initials: C
authors.lastname: Orskov
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D004702:Endocrine Glands / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism*; D005934:Glucagon / Q000378:metabolism*; D052216:Glucagon-Like Peptide 1; D017403:In Situ Hybridization; D007421:Intestine, Small / Q000166:cytology / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism*; D013552:Swine
chemical_list: D010446:Peptide Fragments; D011498:Protein Precursors; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1; D005934:Glucagon