Thermogenic mechanisms and their control.

The alterations in properties of mitochondria and of plasma membrane of brown adipose tissue and skeletal muscle of cold-acclimated rats are reviewed in order to bring out any adaptive changes which are related to the mechanism of nonshivering thermogenesis, and thus to the enhanced calorigenic action of catecholamines known to exist in these animals. Since prevention of the morphological changes in the mitochondria by treatment of the animals with oxytetracycline during acclimation to cold also prevents the development of the enhanced calorigenic response to the catecholamines it is concluded that the changes noted are either a cause of the development of the increased capacity for nonshivering thermogenesis during acclimation to cold or are secondary to the operation of nonshivering thermogenesis.