[Active metabolic processes in resting cells]

A number of intracellular metabolic processes are activated when cells proceed from proliferation to rest. These processes may be classified into 3 main categories: processes regulating the transition of cells from proliferation to rest; metabolic reactions necessary for the suppression of cell proliferation; processes required by a resting cell to maintain viability. Among the last category 2 groups of processes seem to be particularly important: a high rate of macromolecular turnover and an inhancement in the activity of catabolic enzymes. The high rate of RNA and protein turnover prevents the unbalanced cell growth and their death while the enhanced activity of catabolic enzymes maintains partial autolysis of resting cell compensating for the insufficient supply of nutrients due to a decreased external membrane permeability for some low molecular compounds. Thereupon, both these processes provide for the resistance of resting cells against unfavourable ambient effects allowing them to preserve proliferative potentials. Consequently the resting cells are in a special physiological state securing their self-maintenance under conditions of long-lasting absence of proliferation. The ability of cells to pass into a resting state may be regarded as a common feature of living systems acquired in the course of evolution. A co-ordinated activation of certain complexes of metabolic processes appears to be a general principle of resting cells existence in the animate nature.