Abstract
Mammalian hibernation is characterized by distinctive changes in body temperature and metabolism during the course of entry into and arousal from hibernation. Tissues of hibernating animals retain their functional integrity at temperatures well below those at which the same tissues of nonhibernating species cease to function. For example, the heart of the hibernator beats at temperatures near 0°C, while „those of non-hibernating species usually cease at about 10°C (Dawe and Landau, I960; Lyman and Blinks, 1959). Nerves of hibernators conduct at much lower temperatures than do nerves of non-hibernators (Chatfield et al., 1948). Potassium uptake by kidney cortex slices is greater in hibernating rodents than in non-hibernating species such as rats and guinea pigs (Willis, 1964). Moreover, true hibernators possess the ability to spontaneously arouse from the deeply hibernating state without the aid of an external heat source. Thus successful hibernation is characterized by a) the transformation of energy of food stuffs into a usable form (e.g. ATP), b) the coupling of this energy to reactions which are required for maintenance of tissue functional integrity and c) the rapid production of heat from stored energy sources during spontaneous arousal (South, i960). Numerous biochemical studies have been made in an attempt to determine the mechanism(s) v/hereby one species of mammal can hibernate, while closely related species can not. Levels of oxidative enzymes, oxidative phosphorylation efficiency, and in vitro responses of various tissues or enzymes to temperature are among the possible potential mechanisms which have been investigated.