Inducible nitric oxide synthase mediates gut ischemia/reperfusion-induced ileus only after severe insults.
Inducible nitric oxide synthase (NOS 2) is thought to play a role in gut motility disorders that occur under proinflammatory conditions. Clinically, ileus occurs after sepsis and shock-induced gut ischemia/reperfusion (I/R). The purpose of this study was to determine if NOS 2 mediates impaired intestinal transit in well-established models of both moderate and severe gut ischemia/reperfusion. At laparotomy, Sprague-Dawley rats had duodenal catheters placed. Small intestinal transit was determined by quantitating the percentage tracer (FITC-dextran) in 10 equal segments of intestine 30 min after catheter injection [expressed as the mean geometric center (MGC) of distribution]. Transit was assessed at 6 and 24 h after gut ischemia [45 or 75 min of superior mesenteric artery occlusion (SMAO) with sham laparotomy as control]. In a separate set of experiments, N(6)-(iminoethyl)-L-lysine (L-NIL), a selective NOS 2 antagonist, was administered 1 h prior to laparotomy and transit was determined after 6 h as described above. Ileal NOS 2 expression was assessed by Western immunoblot and quantitative "real-time" RT-PCR. We observed that both 45 and 75 min of SMAO decreased intestinal transit at 6 h of reperfusion compared to sham. Ileal NOS 2 mRNA and protein were increased after 75, but not 45, min of SMAO. In addition, L-NIL improved transit after 75, but not 45, min of SMAO. We conclude that (1) NOS 2 is upregulated in the gut only after more severe ischemic insults, and (2) ileus is mediated, at least in part, by NOS 2 under these conditions.
Hassoun
H T
HT
Trauma Research Center, Department of Surgery, Houston Medical School, University of Texas, Houston, Texas 77030, USA.
Weisbrodt
N W
NW
Mercer
D W
DW
Kozar
R A
RA
Moody
F G
FG
Moore
F A
FA
D000818:Animals; D000906:Antibodies; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005769:Gastrointestinal Motility / Q000187:drug effects / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D007415:Intestinal Obstruction / Q000188:drug therapy / Q000378:metabolism*; D007421:Intestine, Small / Q000098:blood supply / Q000201:enzymology*; D008239:Lysine / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000276:immunology; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism*
D000906:Antibodies; D004791:Enzyme Inhibitors; C090663:N(6)-(1-iminoethyl)lysine; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D008239:Lysine