Glutathione and related enzymes in rat liver treated with methyl nitrosourea.

In vivo effects of methyl nitrosourea (MNU) on rat liver glutathione, glutathione S transferase and glutathione reductase have been studied. MNU was injected (20 mg per kg i.r.) weekly for 10 weeks. The animals were killed by decapitation 6 months later, livers were removed, homogenized and the enzymes were studied. Twenty-five animals were treated with MNU. Physiological salt solution was given to ten control animals. It was shown that the cytotoxic effects of MNU cause a decrease of glutathione levels. There was no difference in activity of glutathione reductase in the MNU treated group when compared to control, but glutathione S-transferase activity of the MNU treated group was found to be increased. Glutathione protects the cells against alkylating agents, which may cause cell damage due to depletion of glutathione levels. Increased levels of glutathione S-transferase may be a reaction of the organism to the alkylating agents. Because of depletion of glutathione levels, glutathione reductase levels may be unaffected.