[Functional reserves of the sympathetic apparatus of the heart in hypoxia].

The functional reserves of sympathetic systems, i.e. their capacity to stabilize the level of norepinephrine in the enlarged myocardium of rats exposed to chronic hypoxia, increased with their adaptation to hypoxia and decreased with their deadaptation. The level of these reserves depended at large on the rate of norepinephrine biosynthesis. The degree of myocardial hypertrophy of this genesis increased with prolongation of the hypoxic exposure. It is concluded that optimal supply of norepinephrine to the enlarged heart due to increased functional reserves of sympathetic systems is possible only up to a certain level of an increase in the myocardial mass.