Activation of brown adipose tissue thermogenesis in recovery from anesthetic hypothermia in rats.

Changes of brown adipose tissue (BAT) thermogenesis in the recovery from anesthetic hypothermia were studied by measuring the temperatures of the interscapular BAT and rectum or the tissue uptake of 2-deoxyglucose (2-DG) in rats. After intraperitoneal injection of pentobarbital sodium (50 mg/kg), rectal temperature decreased to reach a steady level of approximately 33 degrees C (steady phase) and then increased gradually (recovery phase). The temperature of the interscapular BAT was significantly higher than rectal temperature in the recovery phase. The uptake of 2-DG in vivo in BAT was low in the steady phase but increased greatly in the recovery phase. The increase in 2-DG uptake was suppressed after surgical sympathetic denervation or when rectal temperature was maintained at approximately 37.5 degrees C. In the heart, skeletal muscle, and white adipose tissue, there was no appreciable change in 2-DG uptake except a slight increase in the heart. beta-Adrenergic blockade attenuated the changes in BAT temperature and 2-DG uptake seen during the recovery phase. It was concluded that BAT significantly contributes to heat production in recovery from anesthetic hypothermia.