Comparative Study of the Temperature Coefficient Q10 of HibernatingGround Squirrels <i>Urocitellus undulatus</i> and Cooled Rats of Different Ages

The temperature coefficients Q10 of heart rate (Q10HR) or oxygen consumption (Q10Ox) were analyzed during the arises from torpor of long-tailed ground squirrels Urocitellus undulatus, as well as during the rewarming of precooled adult rats and rat pups. The Q10Ox value was calculated using a standard equation, whereas for calculating Q10HR, the equation was empirically modified to track changes in this parameter over a wide range of body temperatures (Tb). It was found that during the initial period of rewarming from torpor, at Th ≤ 10 ℃, ground squirrels experienced a sharp increase in the temperature coefficients up to Q10HR = 40 – 50 and Q10Ox = 6 – 7. Even higher values of Q10HR 100 were found at the beginning of rewarming of rat pups, although they had a low level of Q10Ox = 1.2. Adult rats could not withstand cooling below 16 ℃ and demonstrated moderate variability of both Q10HR = 2.0 – 4.0 and Q10Ox = 2.0 – 2.2. During the restoration of normal Tb, the Q10HR in all animals approached the level ~2.0 predicted by the Van't Hoff-Arrhenius rule for chemical reactions in both living and inanimate nature. We assume that high values of Q10HR and Q10Ox, detected in the early period of ground squirrel’s arousal from hibernation, may reveal the functioning of adaptive processes aimed at accelerating body warming. Resistance to cooling and high Q10HR coefficient in the rat pups may indicate rudimentary adaptability to hibernation in the juvenile period of rats, as representatives of the order Rodentia, which also includes natural hibernators such as ground squirrels.