NITRIC-OXIDE - A REGULATOR OF MUCOSAL DEFENSE AND INJURY

There is an abundance of evidence that nitric oxide plays a critical r ole in regulating several components of gastrointestinal mucosal defen se. Suppression of nitric oxide synthesis increases susceptibility to injury, while administration of nitric oxide donors increases resistan ce to injury. On the other hand, nitric oxide has been implicated as a mediator of tissue injury in the gastrointestinal tract during inflam matory reactions. In these cases, the nitric oxide is generally believ ed to be derived from an inducible isoform of nitric oxide synthase. I n this review, we provide an overview of the evidence for and against these dual roles of nitric oxide in modulating gastrointestinal mucosa l defense and injury. We also highlight the potential therapeutic bene fits that may be realized through modulation of tissue nitric oxide le vels.