GUANYLIN, AN ENDOGENOUS LIGAND FOR C-TYPE GUANYLATE-CYCLASE, IS PRODUCED BY GOBLET CELLS IN THE RAT INTESTINE

Background & Aims: Guanylin activates an intestinal guanylate cyclase (GCC) and stimulates electrolyte movement across the gut epithelium. C ells expressing guanylin messenger RNA have been localized to the epit helial cell layer of the intestine; however, the identity of the guany lin-producing cells has not been determined. The aim of this study was to identify cells that express guanylin in the rat intestine. Methods : Antibodies were raised against defined proguanylin epitopes, evaluat ed by Western blotting, and used for immunoperoxidase histochemistry. Results: Guanylin-like immunoreactivity was localized to a subset of g oblet cells. In the small intestine, most, perhaps all, goblet cells i n the villi were immunopositive, as were some goblet cells in upper cr ypts; however, goblet cells deep within crypts were unlabeled. In the colon, goblet cells clustered in the necks and around the openings of crypts were immunopositive, whereas (as in the small intestine) goblet cells in deeper crypt regions were unlabeled. In some animals, immuno reactive columnar epithelial cells were also observed in the colon (al though such cells were not apparent in the small intestine). Relative labeling of columnar cells varied from animal to animal. Conclusions: Guanylin is expressed in mature goblet cells. If secreted in conjuncti on with mucin, it could play a role in the hydration of mucus.