HEPATIC CYTOSOLIC GLUTATHIONE-S-TRANSFERASE ACTIVITIES IN AGING BROWN NORWAY RATS - IMPORTANCE OF SEX-DIFFERENCES AND PHENOBARBITAL TREATMENT FOR STUDIES OF AGING

Age-associated alterations of hepatic cytosolic glutathione S-transferase activities towards 1-chloro-2,4-dinitrobenzene and 1,2-dicholoro-4-nitrobenzene were investigated in Brown Norway rats of both sexes (11-144 weeks old), under control conditions and after administration of phenobarbital. With both substrates, small changes in glutathione S-transferase activities are observed for the control rats (15-53 weeks old). For these specific age groups, male glutathione S-transferase activities are significantly higher than those of their female counterparts, with sex-related differences being most pronounced after 1,2-dichloro-4-nitrobenzene conjugation. Using 1-chloro-2,4-dinitrobenzene as a 'general' substrate, the sex-differences tend to decrease from the age of 53 weeks onwards to become non-significant at the age of 112 weeks. Phenobarbital administration significantly increases the total and the isoenzymes 3-3 and 3-4 activities in both sexes, with the highest and the lowest increase being observed in the youngest and oldest animals, respectively. It therefore can be concluded that some age-related variations exist as far as the glutathione S-transferase activity of both control and phenobarbital-treated rats are concerned, but that the changes observed are rather small. On the contrary, the parameters 'Sex' and 'Phenobarbital treatment' are found to be responsible for the major activity changes observed. © 1990.