Abstract

To study the influence of training, aging and left-ventricular contractility on the sympathetic nervous system, responses of plasma catecholamines and density of adrenoreceptors on intact blood cells were evaluated in 21 dynamically trained subjects, 8 statically trained weight lifters, 15 healthy young and 15 old control subjects, and 55 post-infarction patients. Plasma catecholamines are indicators of the overall sympathetic tone, while the density of adrenoreceptors is a cellular indicator of the sensitivity to catecholamines. Static and dynamic training result in lower catecholamine response at identical work loads during incremental ergometric tests. Higher density of beta2 receptors on intact leucocytes and higher sensitivity to isoproterenol are seen in the dynamically trained test subjects. Higher density of alpha2 receptors on intact thrombocytes is found in the weight lifters. Despite the training-dependent control of the sympathetic activity bradycardia occurs only in endurance-trained subjects, indicating an additionally increased vagal control. The exercise-related tachycardia of the weight lifters, on the other hand, points to an insufficient vagal control of the cardiac sinus rate. Decrease of physical fitness, as related to aging, a deficit in physical training and impaired leftventricular contractility are connected with a higher sympathetic activity at identical work loads and a lower beta-receptor density on intact blood cells and, in cardiac patients, on myocardial cells as well. Changes in the sympathetic system may amplify the age- and disease-dependent decrease of the cardiac function. Results obtained from 20 post-infarction patients after one year of physical therapy point to a significantly improved control of the increased sympathetic activity, related to with a higher stress tolerance. Verf.-Referat