Age and sex related differences in some rat renal NADPH-consuming detoxification enzymes.

Age- and sex-associated changes in some renal drug-metabolizing enzyme activities (NADPH-cytochrome c reductase, the glutathione peroxidase-glutathione reductase system, and thioredoxin reductase) were investigated using male and female Wistar rats (ages ranging from -4 days to 24 months). During aging the activities of NADPH-cytochrome c reductase and thioredoxin reductase showed a marked decrease (approximately 50% in both enzymes compared to adult stage). Glutathione reductase activity presented similar values in adulthood and aging, and glutathione peroxidase activity showed an increase with age (30% compared with the adult values). A marked sex difference was observed in young rats for glutathione peroxidase and thioredoxin reductase activities. However, during aging this difference disappears for glutathione peroxidase activity, but it remains for thioredoxin reductase activity (the specific activity in male old rats was approximately two-fold that obtained from female old rats). The variations in these enzymatic activities may be important when determining the changes in susceptibility of the kidneys to toxic chemicals with aging.