Tonometric assessment of jejunal mucosal nitric oxide formation in anaesthetized pigs

Nitric oxide (NO) in the gut has attracted increasing interest as a regulat ory factor for a wide variety of intestinal functions. This study was perfo rmed to evaluate some methodological aspects and jejunal sources for NO syn thesis. Bench side evaluations and an animal model using chloralose-anaesth etized pigs were used. Immunohistochemistry was performed on samples from p ig intestine and direct measurements of intestinal NO formation were perfor med using intraluminal tonometry. Tonometric measurements were quantitative ly accurate and with high reproducibility. A substantial NO formation was a ssessed which was markedly inhibited by luminal administration of the non-s elective NOS inhibitor L-NAME. Intravenous administration of L-NAME also re duced jejunal NO formation but to a lesser extent. Immunohistochemistry rev ealed staining for the inducible type of NOS in the mucosal surface epithel ium whereas endothelial and neuronal subtypes were located in deeper layers of the jejunal wall. The study argues for that the source of jejunal NO pr oduction, as measured by intraluminal tonometry, is located in close proxim ity with the intestinal mucosa. The NOS in this compartment is predominantl y of the inducible type.