Peptides and exercise at high and low altitudes.

Some peptides are released with stress. We therefore examined effects of different exercise stress at low and moderate altitudes and after heat stress on beta-endorphin and endothelin in the human circulation. We also assessed longitudinally the effects of chronic exertion on beta-endorphin and the relationship to melatonin secretion in well-trained athletes. All peptides and melatonin increased after exercise, but the magnitude of this increase was age-dependent. Chronic exertion is associated with a decrease in exercise induced opioid release and in such individuals melatonin secretion is not beta-endorphin related. Long term high altitude exposure is associated with high-beta-endorphin levels at rest. Atrial natriuretic factor and vasopressin is also released with exercise at moderate altitude. Endothelin, a powerful vasoconstrictor, is increased independent of type of exercise, duration and moderate hypoxia.