EFFECTS OF AGE ON LEVELS OF CYSTEINE, GLUTATHIONE AND RELATED ENZYME-ACTIVITIES IN LIVERS OF MICE AND RATS AND AN ATTEMPT TO REPLENISH HEPATIC GLUTATHIONE LEVEL OF MOUSE WITH CYSTEINE DERIVATIVES

There was a large statistically significant decrease in the hepatic le vel of cysteine and glutathione (GSH) in 24 month-old mice compared to young mice, while, cystine and glutathione disulfide (GSSG) contents in the liver did not differ between young and old mice. Activities of cystathionine gamma-lyase and beta-synthase in mouse liver of the 24 m onth-old group were significantly decreased. In rats, the hepatic leve ls of cysteine, cystine, GSH and GSSG exhibited no statistically signi ficant change during aging to 30 month. As the rats matured, total hep atic activities of both cystathionine gamma-lyase and beta-synthase in creased with maximum levels at 24 months of age and decreased to the s ame level found in 5 week old for the former and to 22% of that in 5 w eek old for the latter. Intraperitoneal administration of diethyl male ate to mice led to depletion of hepatic GSH. When N-acetylcysteine and a thiazolidine derivative were intravenously injected after diethyl m aleate administration, the hepatic GSH level of mice was restored to t he normal level.