Only now, considering the energy costs underlying the life of cells and the organism as a whole, I realized the high cost of adaptation to the changing conditions of the internal environment of the organism. An example is the activation of the synthesis of a large list of enzymes under hypoxic conditions. For example, hypoxia of cell culture of cytotoxic T lymphocytes leads to an increase in the number of more than 7600 proteins [8]. Considering the huge variety of cells involved in the response to hypoxia, a large amount of the body's energy expenditures for adaptation to hypoxia should be assumed.
In my opinion, it is hypoxia that is the most common cause of changes in cell enzymatic patterns. A feature of hypoxia as a leading pathogenic factor is the high frequency of its manifestation in certain local volumes of organs and tissues. With age, the frequency of episodes of local hypoxia, their duration and depth increase, and, therefore, the expenditure of free energy both for adaptation and for exiting the adapted state and return to normoxia, also accompanied by a change in enzymatic patterns, increases.
The constant implementation of such cycles, initiated by episodes of local or general hypoxia, makes the adaptation process the most energy-consuming process that accelerates aging.
Such operational adaptation of the organism to changes in its internal environment occurs not only at the intracellular level, but also at the level of changes in the ratio of cells, one or another specialization. When it is necessary to survive, the body “puts under the knife” even the cells and tissues that are important for it, using them as a full-fledged, operative endogenous nutrition, completely restoring them in conditions of rest, sleep or anabiosis. Thus, deficient oxygen and free energy are also spent on changes in the cellular composition of the body in the process of adaptation.
In this brief review, I will not consider the expenditure of energy for the work of adaptive mechanisms for the consumption of deficient oxygen at the physiological level, which consists in the redistribution of blood between organs and tissues.
In general terms, adaptation is a positive phenomenon, without which life is impossible. But, adaptation is an energy-consuming process. The pathogenic nature of the operational adaptation constantly going on in the body in the cycle: is due to the large additional costs of energy and, accordingly, oxygen, thereby aggravating hypoxia.