[Activity of glutathione peroxidase in rat blood plasma and serum: Postnatal and aging-associated alterations.]

Combining various substrates for assessment of enzymatic activity, we have studied the activity of glutathione peroxidase (GPx) in rat plasma and serum during postnatal ontogeny and aging. During period of weaning, the GPx activity dramatically increases and reaches the almost adult levels to 1,5 months of age. GPx activity is relatively stable in adult rats and retains its high levels in aging rats for a long time. With reduced homocysteine (but not with reduced glutathione) as a GPx substrate, the decrease of GPx activity to 23-26 months of age was revealed. The dramatic increase of GPx activity in plasma from 0,5 to 1-1,5 months of age can be an adaptation to consumption of solid food that may contain the substances inducing oxidative stress. Probably at sufficient consumption of selenium, the decrease of GPx activity in rat plasma occurs only at deep old age and could be considered as an indicator of physiological aging.