Biochemical characteristics of mouse mammary tissues, preneoplastic lesions and tumors

A number of metabolizing systems are measured in normal, preneoplastic and neoplastic mouse mammary tissues derived under three different conditions. These biochemical functions are considered to be important in the activation and detoxification of carcinogens and other xenobiotics and have been linked to the process of rat liver hepatocarcinogenesis. The cytochrome P450-dependent enzyme aminopyrine N-demethylase, consistently depressed in hepatocarcinogenesis models in mouse and rat, does not show a significant change among normal, preneoplastic and neoplastic mammary tissues. Glutathione and the enzymes of glutathione metabolism and utilization (e.g. glutathione-S-transferases and gamma-glutamyl transferase), active in the detoxification of xenobiotics, show no significant differences in carcinogen-induced tumors or in their homologous preneoplasias compared to control tissue. There is no increase in the anionic glutathione-S-transferase, a principal marker in rat hepatocarcinogenesis. The only observed biochemical change was a significant decrease in gamma-glutamyl cysteine synthetase the glutathione synthetic enzyme, in the carcinogen-induced preneoplastic and neoplastic line compared to control. Also inorganic glutathione peroxidase was lower in the preneoplastic, but not in the neoplastic tissues.