Xanthine oxidoreductase activity in human liver disease

The aim of this study was to investigate the level and the form of xanthine oxidoreductase (XOR) in severely diseased human livers, to ascertain whether the modifications of the enzyme activity reported in experimental pathology also occur in human liver disease.

Total, dehydrogenase, and oxidase activities of XOR were measured in samples of human liver removed for transplantation or partial hepatectomy. Samples included four groups: 1) histologically normal liver tissue, adjacent to metastases from extrahepatic tumors (controls), 2) liver with virus-related cirrhosis; 3) liver with virus-negative cirrhosis, and 4) hepatocellular carcinoma tissue (HCC).

The level of total XOR was significantly higher in liver with virus-related cirrhosis, but not in virus-negative cirrhosis, than in controls. In virus-positive cirrhosis, the total XOR activity correlated positively with the level of ALT. The percentage of XOR oxidase activity in cirrhotic liver, regardless of virus infection, correlated positively with aspartate amino-transferase, bilirubin concentration, and partial thromboplastin time, and negatively with prothrombin time. The activity of XOR was significantly lower in HCC than in control tissue or in a nonneoplastic area of the same liver.

Consistent with previous reports in experimental pathology, the level of XOR was increased in cirrhotic liver, in association with viral infection. This increment correlated with ALT, suggesting a relationship between XOR activity and the extent of liver injury caused by viral replication. The percentage of oxidase activity seems to be correlated with tissue damage and consequent liver impairment. The low XOR activity observed in HCC is consistent with reported experimental pathology.