Thermogenic mechanisms in cold-acclimated animals.

1. This paper reviews the mechanisms of thermogenesis after cold-acclimation. 2. Upon exposure to cold, the oxygen consumption of animals increases by means of shivering and non-shivering thermogenesis. As cold exposure progresses, shivering decreases while non-shivering thermogenesis increases, so that the cold-acclimated animal produces heat mostly by non-shivering thermogenesis. 3. Brown adipose tissue in several species, including man, is an essentially thermogenic organ that produces heat by uncoupling mechanisms in mitochondria. 4. The activity of brown adipose tissue can be assessed by physiological and biochemical methods. 5. After cold acclimation, the activity and mass of brown adipose tissue are higher than in control animals. Brown adipose tissue is considered the main factor responsible for non-shivering thermogenesis.