Effects of air temperatures on antioxidant defense and immunity in Mongolian gerbils

Temperature influences many physiological processes including antioxidant defense and immunity. The hypothesis that air temperatures has no effects on antioxidant defense and innate immunity in Mongolian gerbils (Meriones unguiculatus) was tested. Thirty-three male gerbils were randomly divided into the 4 °C (n = 11), 23 °C (n = 11) and 32 °C groups (n = 11), in which the treatment course lasted for 27 days. We found that air temperatures had no effects on body mass. At lower temperature, gross energy intake and the masses of most organs were higher, whereas fat free dry carcass and body fat were lower. H₂O₂ titres increased in liver but decreased in small intestine, and remained unchanged in heart, kidney and testis upon cold exposure. At lower temperature, malonaldehyde (MDA) content was higher in the liver, lower in kidneys and testis, and did not differ in the heart and small intestine. The activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC) in liver were higher in 4 °C group than 23 °C group, while liver catalase (CAT) activity was lower in the 4 °C group than in the 23 °C group. No significant difference was observed in the activities of SOD, CAT and T-AOC in the heart, kidney, testis and small intestine among the 4 °C, 23 °C and 32 °C groups. As expected, bacteria killing capacity indicating innate immunity, white blood cells and thymus mass were all not affected by air temperatures. Similarly, air temperatures had no effect on the levels of testosterone and corticosterone, both of which were not correlated with innate immunity, H₂O₂ and MDA levels, the activity of SOD, CAT, and T-AOC in all the detected tissues. In conclusion, air temperature affected antioxidant capacity, but not immune responses or serum concentrations of corticosterone and testosterone. Overall, up-regulation or maintenance of antioxidant defenses and immunity might be an important mechanism for gerbils to survive highly variable temperature.