Possible role of certain antioxidant enzymes in dimethy lnitrosamine‐induced liver carcinogenesis

An investigation was carried out to establish whether the reduction in catalase, glutathione peroxidase and superoxide dismutase activity, normally observed in liver tumours, is an early event and therefore of pathogenetic importance, or whether it is a late occurrence. Experiments performed on dimethylnitrosamine‐treated hepatectomized and non‐hepatectomized rats show that the decrease in activity of these enzymes is entirely due to hepatectomy, since the tumourinducing doses of dimethylnitrosamine failed to provoke variations in the activity of these enzymes, in either normal or regenerating liver.