Rat guanylin cDNA: characterization of the precursor of an endogenous activator of intestinal guanylate cyclase.

Guanylin is a recently discovered endogenous activator of intestinal guanylate cyclase that was purified from intestinal tissue. Clones have been isolated which demonstrate that the guanylin peptide is contained within a 115 amino acid apparent preprohormone encoded by a 600 base messenger RNA in rat jejunum. The messenger RNA is found predominantly in intestinal tissues, showing a striking gradient of expression ranging from undetectable in esophagus and stomach to abundant in colon. Guanylin may serve a paracrine function to regulate intestinal guanylate cyclase activity, cyclic GMP levels, and thereby, fluid and electrolyte absorption. We hypothesize that the heat stable enterotoxins mimic the endogenously produced guanylin to cause diarrhea.