Abstract
Summary
Plasma GH concentration, as estimated by radioimmunoassay increased significantly in cattle during 4 hr of acute thermal exposure. Blood hematocrit and plasma specific gravity did not change, while rectal temperature increased markedly. However, the rise and decline in plasma GH levels following, respectively, the onset and cessation of thermal exposure preceded the changes in body temperature. Changes in plasma GH were abrupt with the onset of heat exposure and correlated significantly with environmental temperatures suggesting the neural involvement of the skin thermal receptors, and areas of the hypothalamus. The possible adrenergic mechanism and significance of GH secretion during acute thermal stress is discussed.
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