Epithelial barrier integrity and intraluminal nitric oxide production in response to acid perfusion of the ferret oesophagus

Aim: To evaluate the source and role of acid-induced intraluminal nitric oxide (NO) production in the oesophagus by studying how the exposure of the oesophagus to acid affects NO release, via the NO-producing enzyme NO synthase and its relation to changes in epithelial barrier integrity. Methods: Ferrets were anaesthetized and their oesophagi were divided at both ends. The test subjects were pre-treated with the intravenous NO synthase inhibitors NG-nitro-l-arginine-methyl ester (l-NAME, 100 mg kg−1) and 1400W (12 mg kg−1). Untreated and NG-nitro-d-arginine-methyl ester pre-treated (d-NAME, 100 mg kg−1) animals served as controls. The oesophagus was then perfused with either HCl (0.1 m) or physiological saline for 20 min. The intraluminal NO concentration was determined before and after the acid/saline infusion while the transmucosal potential difference (PD) was monitored continuously. Oesophageal biopsies were examined for expression of inducible NO synthase using immunohistochemistry. Results: The intraluminal NO concentration increased after acid exposure. This was blocked by l-NAME and 1400W, but not by d-NAME. The peak PD response was not affected by agents affecting NO synthesis, while the plateau response was attenuated by l-NAME, d-NAME and 1400W. Immunohistochemistry revealed inducible NO synthase expression in the epithelium. Conclusions: Exposing the ferret oesophageal mucosa to acid elicited an increase in juxtamucosal NO formation through the activation of inducible NO synthase. The corresponding electrophysiological observations suggested an association between mucosal NO production and epithelial integrity.