Temporal expression of hepatic inducible nitric oxide synthase in liver cirrhosis.
OBJECTIVE
Nitric oxide (NO) has been implicated in the pathogenesis of liver cirrhosis. We have found inducible nitric oxide synthase (iNOS) can be induced in hepatocytes of cirrhotic liver. This study further investigated the temporal expression and activity of hepatic iNOS in cirrhosis development.


METHODS
Cirrhosis was induced in rats by chronic bile duct ligation (BDL). At different time points after the operation, samples were collected to examine NO concentration, liver function, and morphological changes. Hepatocytes were isolated for determination of iNOS mRNA, protein and enzymatic activity.


RESULTS
Histological examination showed early cirrhosis 1-2 wk after BDL, with advanced cirrhosis at 3-4 wk. Bilirubin increased dramatically 3 d after BDL, but decreased by 47% on d 14. Three weeks after BDL, it elevated again. Systemic NO concentration did not increase significantly until 4 wk after BDL, when ascites developed. Hepatocyte iNOS mRNA expression was identified 3 d after BDL, and enhanced with time to 3 wk, but reduced thereafter. iNOS protein showed a similar pattern to mRNA expression. iNOS activity decreased from d 3 to d 7, but increased again thereafter till d 21.


CONCLUSIONS
Hepatic iNOS can be induced in the early stage, which increases with time as cirrhosis develops. Its enzymatic activity is significantly correlated with protein expression and histological alterations of the liver, but not with systemic NO levels, nor with absolute values of liver function markers.
Wei
Chang-Li
CL
Department of Biochemistry, Faculty of Medicine, National University of Singapore, 119260, Singapore.
Hon
Wei-Min
WM
Lee
Kang-Hoe
KH
Khoo
Hoon-Eng
HE
D000818:Animals; D022781:Hepatocytes / Q000201:enzymology; D008099:Liver / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D008106:Liver Cirrhosis, Experimental / Q000201:enzymology* / Q000473:pathology / Q000503:physiopathology; D008297:Male; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat