The guanylin/STa receptor is expressed in crypts and apical epithelium throughout the mouse intestine.

Guanylyl cyclase C (GC-C), a transmembrane receptor for E. coli heat-stable enterotoxin (STa) and for the endogenous peptides guanylin and uroguanylin, catalyzes formation of cGMP and influences fluid and electrolyte flux in the gut. We characterized the expression of GC-C in the mouse by Northern blot, in situ hybridization, and ligand binding studies. GC-C mRNA was present in mouse intestine by embryonic day 12, and was expressed at high levels in both crypts and villus or surface epithelium of adult small intestine and colon, respectively. Radiolabeled STa binding to membranes from several tissues correlated with the presence of GC-C mRNA. Extraintestinal GC-C expression was detected only in neonatal mouse liver. The presence of GC-C in mouse intestinal crypts supports the putative role of GC-C in fluid and electrolyte homeostasis and resembles the pattern in human tissues.