Effects of age and dietary restriction on liver glutathione transferase activities in Lobund-Wistar rats.

Glutathione-S-transferases (GST) are a group of enzymes which detoxify electrophilic xenobiotics (including drugs, carcinogens and their metabolites), and thus may be involved in the age-related pathologic process. Effects of a 30% dietary restriction on liver GST activities toward seven substrates were studied in male Lobund-Wistar (L-W) rats at 6, 12, 18, 24 and 30 months of age. The enzyme activities in the ad libitum (AL) group toward 1-chloro-2,4-dinitrobenzene (CDNB), bromosulfophthalein (BSP), 4-nitropyridine-N-oxide (NPNO), p-nitrobenzyl chloride (NBC), trans-4-phenyl-3-buten-2-one (PBO) and styrene oxide (STOX) did not change with age, while those toward 1,2-dicholoro-4-nitrobenzene (DCNB) decreased after middle age. The enzyme activities in the dietary restricted (DR) group toward CDNB and STOX did not change with age, while those toward DCNB, BSP, NPNO, NBC and PBO decreased after middle age. The DR group had significantly higher GST activities than the AL group, especially at 18 months, when BSP, NPNO, NBC and PBO were used as the substrates. Dietary restriction did not affect GST activities toward all seven substrates at old age. These results are substrate-specific, indicating that isozyme-specific changes in GST activities occur with dietary restriction and aging. The results suggest that dietary restriction enhances liver detoxification capability associated with GSH conjugation in middle age, which may contribute to the delaying of the age-related pathologic process until a later point in life in this animal model.