Changes in the Activity of Glutathione Peroxidase in the Blood Plasma and Serum of Rats during Postnatal Development and Aging

Resumo

The activity of glutathione peroxidase (GPx) in plasma and serum of Wistar rats during postnatal ontogeny and aging is studied. A combination of various substrates is used for assessment of the enzymatic activity. During the period of milk nutrition, since the beginning of the consumption of solid food, GPx activity is rapidly increasing and almost reaches the adult level by 1.5 months. Enzyme activity remains stable in adulthood and has long been high in aging rats. A decrease in GPx activity around 23–26 months of age is revealed, with reduced homocysteine (but not with reduced glutathione) as a GPx substrate. The dramatic increase of GPx activity in plasma from 0.5 to 1–1.5 months of age may be an adaptation to consumption of solid food that may contain substances inducing oxidative stress. Probably, with sufficient selenium consumption, a decrease in GPx activity in rat plasma occurs only in extreme old age and can be considered as an indicator of physiological aging.