IMMUNOHISTOCHEMICAL LOCALIZATION OF GUANYLIN IN THE RAT SMALL-INTESTINE AND COLON

Guanylin is an endogenous mammalian ligand which binds to guanylate cy clase C(GC-C), the Escherichia coli heat-stable enterotoxin receptor. This interaction results in intestinal Cl- and fluid secretion, which is largely, if not exclusively, mediated through the cystic fibrosis t ransmembrane regulator (CFTR). Using in situ hybridization, we have pr eviously localized guanylin mRNA to villus epithelial cells of the rat small intestine and to superficial epithelial cells of the rat colon. In the present study, we demonstrate immunoreactive guanylin in a sub population of goblet cells in the rat jejunum and ileum. In the colon, there was immunostaining of superficial epithelial cells and goblet c ells. The immunohistochemical localization of guanylin parallels the o bserved distribution of guanylin mRNA. Localization of guanylin in gob let cells leads us to speculate that an in vivo function of guanylin r egulated, CFTR-mediated Cl- secretion is to hydrate intestinal mucin. (C) 1995 Academic Press, Inc.