Effect of adaptation to high-altitude hypoxia and physical load on the variability of the heart rhythm and force of the contractions
Pshennikova, M.G.; Giber, L.M.; Zakharov, M.I.
Kardiologiia 19(2): 105-107
1979
ISSN/ISBN: 0022-9040 PMID: 423428 Document Number: 153962
Experiments were performed on white male rats adapted to high-altitude hypoxia and physical exertion to study the variability in rhythm and force of cardiac contraction and the fluctuation of these factors during maximum stress induced by total aortal ligation. Systolic pressure in the left ventricle was monitored by ECG, measuring the force of myocardial contraction. Contractile function was recorded during intact cardiac self-regulation and after pharmacological blocking of adrenergic regulation and after vagotomy. Adaptation to high-altitude hypoxia was a stabilizing factor and aided in the heart's rapid transition to a new level of operation in response to stress. Adaptation to physical exertion also helped to stabilize the parameters of cardiac contractile function during maximum isometric stress. A principal role in this stabilization effect may be played by the restructuring of the sympathoadrenal system, characterized by increased resistance of the adrenergic mechanisms of cardiac regulation to stress and decreased production of catecholamines by the adrenal glands and sympathetic endings in response to stress.