Nitric oxide: an ubiquitous actor in the gastrointestinal tract.

The digestive system is one of the major sources of nitric oxide, which, due to its smooth muscle-relaxing and vasodilating properties, appears to play a key role in the regulation of gastrointestinal motility, mucosal blood flow and gastroprotection. In addition nitric oxide takes part in the control of pancreatic secretion and liver functions. Recent studies suggest that the substance may be involved in the pathogenesis of achalasia, toxic megacolon, Hirschsprung's disease and portal hypertension.