Seasonal changes in the antioxidative defense in ground squirrels (Citellus citellus): possible role of GSH-Px.

As seasonal hibernators, ground squirrels decrease their body temperature to 7 degrees C and hibernate during the winter. Maintenance at 30 degrees C prevents seasonal changes of body temperature and animals remain euthermic and active. We measured selenium (Se)-dependent glutathione peroxidase (GSH-Px), as well as the activity of other antioxidative components such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione-S-transferase (GST) and the amount of low-molecular-weight antioxidants glutathione (GSH), ascorbic acid (AsA), and vitamin E (vit E) in spring, summer, and winter in ground squirrels continuously kept at a temperature of 30 degrees C. We examined liver and interscapular brown adipose tissue (IBAT) as thermogenic tissues, as well as the brain and the kidneys. During the winter, we found a decrease in enzymatic activity and an increase in the level of low molecular antioxidants in all tissues. Correlation analysis revealed a similarity in the composition of antioxidative defense (AD) among the tissues examined. The results obtained clearly demonstrated numerous correlative expressions of antioxidative components in this experimental model, especially of GSH-Px, suggesting the complexity of the system responsible for the maintenance of physiological homeostasis.