- Vibrio cholerae (cholera toxin) causes diarrhea by stimulating Cl- secretion.
- Cholera toxin binds to receptors in the luminal membranes of crypt cells and activates adenylate cyclase in the basolateral membrane.
- Intracellular cAMP increases; as a result, Cl- channels in the luminal membrane open.
- Na+ and H2O follow Cl- into the lumen and lead to secretory diarrhea.
- Some strains of Escherichia coli cause diarrhea by a similar mechanism.