Differential nitric oxide synthase expression during hepatic ischemia-reperfusion.
BACKGROUND
In recent years the important role of nitric oxide in hepatic ischemia-reperfusion injury has been increasingly recognised. The prevailing consensus is that reperfusion injury may be partly the result of decreased production of nitric oxide from endothelial nitric oxide synthase and excessive production of nitric oxide from the inducible isoform. We therefore undertook this study to characterize the expression of different nitric oxide synthase isoforms during hepatic reperfusion.


METHODS
Male Wistar rats (n = 6) were subjected to 45 minutes of partial hepatic ischemia (left lateral and median lobes) followed by 6 hours of reperfusion. Control animals (n = 6) were subjected to sham laparotomy. The expression of endothelial and inducible nitric oxide synthase was examined using immunohistochemistry and Western blotting. Liver sections were also stained with nitrotyrosine antibody, a specific marker of protein damage induced by peroxynitrite (a highly reactive free radical formed from nitric oxide).


RESULTS
Liver sections from all the control animals showed normal expression of the endothelial isoform and no expression of inducible nitric oxide synthase. Livers from all the animals subjected to hepatic ischemia showed decreased expression of endothelial nitric oxide synthase, and all but one animal from this group showed expression of the inducible isoform both in inflammatory cells and in hepatocytes. Western blotting confirmed these findings. Staining with the antinitrotyrosine antibody was also confined to five liver sections from animals subjected to hepatic ischemia.


CONCLUSIONS
During the reperfusion period after hepatic ischemia, endothelial nitric oxide synthase is downregulated while inducible nitric oxide synthase is expressed in both hepatocytes and inflammatory cells. The presence of nitrotyrosine in livers subjected to hepatic ischemia-reperfusion suggests that the expression of inducible nitric oxide synthase plays an important role in mediating reperfusion injury in this model.
Serracino-Inglott
Ferdinand
F
Division of Surgery, Anesthetics and Intensive Care, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom. fsinglott@hotmail.com
Virlos
Ioannis T
IT
Habib
Nagy A
NA
Williamson
Robin C N
RC
Mathie
Robert T
RT
D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D005455:Fluorescent Antibody Technique / Q000379:methods; D007511:Ischemia / Q000201:enzymology* / Q000473:pathology; D008099:Liver / Q000098:blood supply* / Q000201:enzymology / Q000473:pathology; D008107:Liver Diseases / Q000201:enzymology* / Q000473:pathology; D008111:Liver Function Tests; D008297:Male; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000201:enzymology* / Q000209:etiology / Q000473:pathology; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat