Age-Related Changes in the Tissue Antioxidant System of Canids

The study was aimed at determining tissue antioxidant levels in three closely related albeit ecologically different Canidae species: the raccoon dog (Nyctereutes procyonoides), silver fox (Vulpes vulpes) and blue fox (Vulpes lagopus), aged 0.5 (juvenile), 1.5–3.5 (adult) and 4.5–5.5 (aging) years. Some tested parameters were found to be species-specific: as compared to other species, raccoon dogs and blue foxes exhibited higher α-tocopherol levels in the liver and kidney, blue foxes were characterized by a higher activity of the antioxidant enzymes in the kidneys, while silver foxes had higher glutathione (GSH) levels in the liver, kidneys and heart. The antioxidant defense system in all organs of the tested species was distinguished by a relative stability. In raccoon dogs, the retinol level in the heart increased with age, while in silver foxes it is only superoxide dismutase (SOD) activity in the kidneys and the GSH level in the liver and heart that underwent significant changes with age. In blue foxes, aging was accompanied by an increase in liver retinol and kidney α-tocopherol levels as well as a decrease in the kidney GSH level. Besides, sex differences were found in antioxidant levels in blue foxes. Our results are consistent with the data obtained by other authors for other animal species, indicating a mixed pattern of age-related changes in the antioxidant defense system of carnivorous canids. While some antioxidants rise and the other fall, the functionality of the whole system does not appear to be disturbed. Ecological and physiological features of different mammalian species may determine the adaptive potential of animals and affect the tested indicators of the antioxidant defense system during late postnatal ontogenesis.