PLASMA GLUCOSE, LACTATE AND FREE FATTY ACID RESPONSES TO ADRENALINE IN CHRONICALLY WARM- AND COLD-EXPOSED SHEEP

Abstract

The effects of chronic cold exposure, fasting, or both on the plasma metabolite responses to jugular infusions of adrenaline were studied in eight five-mo-old wether lambs. Following maintenance at 20–22 °C or −4 to 10 °C for 2–3 wk the sheep received adrenaline infusions (0.15 μg∙kg−1∙min−1) for 75 min prior to and following a 72-h fast. Plasma samples collected at intervals of 10–15 min before and during adrenaline infusion were analyzed for glucose, lactate and total free fatty acids. Chronic cold exposure had no effect on the pre-infusion plasma glucose, lactate or free fatty acid concentrations. Fasting decreased plasma glucose and lactate and increased plasma free fatty acid concentrations. The plasma glucose response to adrenaline was greater (P < 0.01) in cold- than warm-exposed sheep and fasting depressed this response to a greater extent in the cold-exposed sheep. The plasma lactate response to adrenaline was not influenced by temperature treatment or fasting. Both groups of fasted sheep showed a large increase in plasma free fatty acids during adrenaline infusion but when fed the response was minimal.