Urinary Excretion of Adrenaline and Noradrenaline in Cattle During Heat and Cold Exposure

The effects of cold and heat exposure upon the urinary excretion of adrenaline and noradrenaline were studied in the climatic laboratory on nonlactating cattle. The experimental animals were kept in a climatic chamber at 18 C for 3 weeks, then exposed for 48 hours to 18, 2, 18, 37, and 18 C. When the cows were exposed to 37 C, urinary excretion of noradrenaline increased significantly from 59 μg/24 hours at 18 C to 71.6 μg/24 hours at 37 C. The mean adrenaline excretion was not affected. During exposure at 2 C, excretion of noradrenaline was significantly increased. At 18 C, urinary excretion was 58.8 μg/24 hours as compared with 71.3 at 2 C. Excretion of adrenaline was not significantly affected. Heat and cold exposures increased the release of noradrenaline by the sympathetic nerve endings without activation of the adrenal medulla.