Epinephrine and norepinephrine related to cardiorespiratory and metabolic changes in calves during physical exercise

Experiments were designed to study changes of blood levels of norepinephrine (NE) and epinephrine (E) and their possible role in metabolic adaptation to short-lasting physical exercise in calves. After a resting period for 5 min (I), animals walked on a treadmill for 10 min at a speed of 60 m/min, first horizontally for 5 min (II), then at a slope of 6 degrees for another 5 min (III), followed by a recovery period for 5 min (IV). Levels of NE and E increased within minutes during walking and then decreased. Changes were closely related to respiration rate, ventilation volume, O2-uptake, heart rate and blood lactate levels. Blood triiodothyronine and protein slightly increased only during period III, whereas glucose, non-esterified fatty acids and the respiration quotient increased throughout the experiment. Blood insulin levels were decreased during walking and rapidly increased afterwards. Blood glucagon did not change significantly. Work load affected all parameters except glucagon and triiodothyronine. There were individually significant differences for all parameters, except for NE and the respiration quotient. The data demonstrate rapid reactions of the cardiorespiratory system and of blood insulin and lactate levels on submaximal work load, normally in close association with plasma E and NE.