Effect of long-term exposure to cold on the antioxidant defense system in the rat.

Catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), and glutathione-S-transferase (GST) activities as well as glutathione (GSH), ascorbic acid (AsA), and vitamin E concentrations were analyzed in the blood, liver, brain, interscapular brown adipose tissue (IBAT), and small intestine of rats exposed to low environmental temperature (4 degrees C; 35, 75, and 105 d of exposure) and in controls of the same age exposed to an environmental temperature of 22 +/- 2 degrees C. Prolonged cold exposure resulted in an increase in GSH-Px in IBAT and in small intestine after 35, 75, and 105 d of exposure. Catalase activity in cold-exposed animals was higher in IBAT after 75 and 105 d of cold exposure. Glutathione reductase activity was greater in brain after 35 d, in liver after 75 d, and in IBAT after 105 d of exposure to low temperatures as compared to the controls. In contrast, GST activity was lower in liver and IBAT after 35 and 75 d of cold exposure. AsA and GSH (determined only 105 d after cold exposure) were markedly higher in IBAT, whereas plasma GSH was lower and plasma AsA was higher in cold-exposed animals. The observed changes in analysed components of the antioxidant defense system under conditions of prolonged exposure to low temperature suggest that a reorganization the activity of this system at the molecular level occurred. Although other studies indicate that a 21-d cold exposure is sufficient for adaptation of thermogenesis, the present study shows that in general, longer periods are required for the registration of the changes in the antioxidant defense system.