Beneficial effects of inducible nitric oxide synthase inhibitor on reperfusion injury in the pig liver.
BACKGROUND
Although inhibition of endothelial nitric oxide synthase (eNOS) has been reported to aggravate hepatic ischemia-reperfusion (I/R) injury, the role of inducible nitric oxide synthase (iNOS) has been still unknown. We investigated the role of NO produced by iNOS, and evaluated the effect of an iNOS inhibitor on prolonged warm I/R injury in the pig liver.


METHODS
Pigs were subjected to 120 min of hepatic warm I/R under the extracorporeal circulation. We investigated the time course of changes in serum and hepatic microdialysate NO2- + NO3- (NOx) and the cellular distribution of eNOS and iNOS by immunohistochemistry, including a double-immunofluorescence technique in combination with confocal laser scanning microscopy. The effect of iNOS inhibitor was also investigated.


RESULTS
Hepatic I/R induced new nitric oxide production in serum and hepatic microdialysate NOx after reperfusion and severe hepatic damage in the centrilobular region where nitrotyrosine was strongly expressed. Diffuse eNOS expression in sinusoidal endothelium did not differ before and after reperfusion. In contrast, strong iNOS expression in Kupffer cells and neutrophils appeared strongly in the centrilobular region after reperfusion. Pigs with intraportal administration of N(G)-nitro-L-arginine (10 mg/kg) died during the period of ischemia or early in the period of reperfusion with a high mortality rate (80.0%). Intraportal administration of aminoguanidine hemisulfate (10 mg/kg) significantly suppressed nitric oxide production and serum aspartate aminotransferase after reperfusion, inhibited nitrotyrosine expression, and attenuated hepatic damage.


CONCLUSIONS
These results indicate that hepatic I/R injury is triggered by centrilobular iNOS expression; and attenuated by inhibition of iNOS.
Isobe
M
M
Department of Surgery, Sapporo Medical University School of Medicine, Japan.
Katsuramaki
T
T
Hirata
K
K
Kimura
H
H
Nagayama
M
M
Matsuno
T
T
D000818:Animals; D001158:Arteries; D001219:Aspartate Aminotransferases / Q000097:blood; D001794:Blood Pressure; D005260:Female; D005455:Fluorescent Antibody Technique; D008099:Liver / Q000098:blood supply* / Q000737:chemistry / Q000201:enzymology; D018613:Microscopy, Confocal; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D015427:Reperfusion Injury / Q000401:mortality; D015996:Survival Rate; D013552:Swine; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis
C002744:3-nitrotyrosine; D014443:Tyrosine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D001219:Aspartate Aminotransferases