Effect of adaptation to altitude on the myocardial noradrenaline content and on the resistance of adrenergic mechanisms to acute cardiac overload in rats.

Abstract

The changes of the myocardial noradrenaline concentration and that of protein synthesis in sympathetic neurons innervating the heart were studied in male Wistar rats during adaptation to simulated altitude. Adaptation to hypoxia was achieved by placing animals in a low pressure chamber daily for 5 to 6 hours 5 days a week up to 7.000 m for 11 weeks. After 10 days of exposure a decrease of the noradrenaline concentration in the myocardium was observed, but later the concentration began to increase again and returned to normal values in spite of the altitude stress. The recovery of the noradrenaline concentration was accompanied by an activation of protein synthesis in sympathetic neurons and glial cells of the stellate ganglia innervating the heart. The effect of the preliminary adaptation to simulated altitude was studied in rats with acute cardiac overload produced by aorta coarctation. The preliminary adaptation to hypoxia prevented greatly the reduction in cardiac noradrenaline concentration that usually occurred in control animals in acute cardiac overload.