Guanylin

Guanylin is a 15 amino acid polypeptide that is secreted by goblet cells in the colon. Guanylin acts as an agonist of the guanylyl cyclase receptor GC-C and regulates electrolyte and water transport in intestinal and renal epithelia. Upon receptor binding, guanylin increases the intracellular concentration of cGMP, induces chloride secretion and decreases intestinal fluid absorption, ultimately causing diarrhoea. The peptide stimulates the enzyme through the same receptor binding region as the heat-stable enterotoxins.