PARTICIPATION OF SKELETAL MUSCLE AND KIDNEY DURING NONSHIVERING THERMOGENESIS IN COLD-ACCLIMATED RATS

Abstract

The oxygen consumption of the partly isolated leg muscles and of the kidney was measured in situ in cold-acclimated rats before and during exposure to cold or during noradrenaline infusion. All rats had been anesthetized with sodium barbital and those exposed to cold had been fully curarized to prevent muscle activity. During cold exposure and noradrenaline infusion oxygen consumption of the rats was approximately doubled, and the oxygen consumption of leg muscles was approximately doubled without increase in blood flow. No increase in oxygen consumption was observed in the kidney during exposure to cold or noradrenaline infusion in spite of an increase of 75% in the oxygen consumption of the whole animal. Direct evidence for significant participation of striated muscles in non-shivering thermogenesis has thus been obtained. However, it appears unlikely that the maximal potential increase in oxygen consumption of cold-acclimated rats at very low temperatures could be attributed solely to the metabolic activity of skeletal muscles.