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.