Role of inducible nitric oxide synthase in postoperative intestinal smooth muscle dysfunction in rodents.
OBJECTIVE
We have shown that intestinal manipulation leads to a significant inhibition of circular muscle contraction. We hypothesized that the inflammatory mediator inducible nitric oxide (NO) plays a role in surgically induced ileus.


METHODS
Rats and inducible NO synthase (iNOS) knockout and wild-type mice underwent a simple intestinal manipulation. Reverse-transcription polymerase chain reaction and immunohistochemistry were used to detect and localize iNOS expression. Nitrite and NO production were measured in muscularis cultures. Spontaneous and bethanechol-stimulated jejunal circular muscle contractions were measured in an organ bath.


RESULTS
Intestinal manipulation resulted in significant iNOS messenger RNA induction in mucosa and muscularis. Immunohistochemistry localized iNOS in phagocytes within the muscularis. Nitrite and NO production increased 59.8-fold 24 hours after manipulation. L-n(6)-(1-iminoethyl) lysine (L-NIL) inhibited this response. In control rats, selective iNOS inhibition did not increase spontaneous muscle activity, but after manipulation L-NIL significantly improved spontaneous activity. iNOS knockout mice showed a significant 81% decrease in neutrophil infiltration into the muscularis after intestinal manipulation compared with wild-types. Contractile activity was normal in knockout mice after intestinal manipulation.


CONCLUSIONS
These results show that leukocyte-derived inducible NO inhibits gastrointestinal motility after manipulation and plays an essential role in the initiation of intestinal inflammation.
Kalff
J C
JC
Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania 15261, USA.
Schraut
W H
WH
Billiar
T R
TR
Simmons
R L
RL
Bauer
A J
AJ
D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000502:physiology* / Q000503:physiopathology / Q000601:surgery*; D008239:Lysine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000502:physiology / Q000503:physiopathology / Q000601:surgery; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D010586:Phagocytes / Q000201:enzymology; D051381:Rats; D011912:Rats, Inbred ACI
D004791:Enzyme Inhibitors; C090663:N(6)-(1-iminoethyl)lysine; D009573:Nitrites; D018723:Bethanechol; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C496318:Nos2 protein, rat; D008239:Lysine