The characteristic symptoms of cholera are extensive loss of body fluids and Na+ through continuous debilitating diarrhea that can lead to severe dehydration. If untreated, the disease is often fatal. The underlying cause of the symptoms is the ADP-ribosylation of an arg residue on the a subunit of a GS protein by cholera toxin. Based on the above information, propose a normal function for cAMP in intestinal epithelial cells and suggest a possible treatment for cholera.