Age-Related Changes in the Tissue Antioxidant Defense of the Northern Birch Mouse (Sicista betulina, Rodentia) at the Northern Periphery of Its Range

The study is aimed at determining tissue antioxidant levels in juvenile and adult northern birch mice (Sicista betulina Pallas, 1779) at the northern periphery of its range (Republic of Karelia). Our results indicate a mixed pattern of age-related changes in the antioxidant defense system: aging is accompanied by a decrease in catalase activity in the kidneys as well as an increase in heart catalase activity and kidney, cardiac, and skeletal muscle superoxide dismutase activity. The levels of low-molecular antioxidants, i.e., reduced glutathione (GSH) (kidneys and heart) and α-tocopherol (heart and skeletal muscle), are lower in juvenile northern birch mice compared to adults animals, which is probably associated not only with the active growth and high mobility of juvenile mice during the dispersal period, but also with the stress of physiological systems due to living in northern conditions and preparing for hibernation. Higher levels of GSH and α-tocopherol are found in the hearts of adult northern birch mice compared to other small mammal species of the order Rodentia living in the Republic of Karelia, which indicates the important role of low-molecular weight antioxidants in protecting tissues against oxidative damage in this species.