Endothermy of organisms and subcellular mechanisms of thermogenesis

Abstract

It is generally known that mammals and birds are warm-blooded, and they are able to maintain such a state is not only in comfort, but in low and high temperature conditions. These circumstances, in all probability, were the prerequisite for the development of ideas about the existence of an organism of warm-blooded special heat generating system. Currently, it was accumulated a lot of material in this direction, which shows that heat production is determined by subcellular specialized mechanisms. It possesses various activities that differs significantly in phylogenetically different classes of vertebrates, in ontogenesis of mammals and birds at various states of an organism. Therefore, warm-blooded animals were allocated to a separate group possessing a high metabolism and support constant and high (about 36°C-40°C) body temperature. The other group includes cold-blooded animals with low metabolism and changeable body temperature. To classify animals according to temperature status in modern literature it is widely used a term of “warm-blooded and cold-blooded”, “homoeothermic and poikilothermic”, “ectothermic and endothermic” animals. In practice, these groups are terms often used interchangeably although they have different meaning. We will also use them in unequivocal terms, although we mainly use a term of “ectothermia and endothermia”. Differences in the level of metabolism between endo-and ectothermic organisms on average in 10 times, but in some cases it reaches up to 100 or more times.1–10 This comparison shows that maintaining of the endothermic state is achieved by a high cost. Possible, up to 90%, and sometimes most of the metabolism is spent only on heat production to maintain the endothermic state of the body. Krogh11 is one of the first to notice lower metabolic rate in cold-blooded animals compared to the warmblooded. However, it took a long time to fully clarify the question about the difference between cold and warm-blooded organisms in metabolism and heat production.