ABSTRACT
In most smaller mammals, brown adipose tissue produces much of the heat needed for keeping warm in the cold and much of the heat needed for the arousal after each hibernation bout. Adrenergic stimulation of brown-fat cells leads to thermogenesis via a pathway, much of which is known. Whereas the animal does make better cells, its main endeavour is to increase the number of brown fat cells, in order to oppose the hazards of living in the cold. If thermogenesis in brown-fat cells is directly stimulated with exogenous fatty acids, cells from cold-acclimated and control animals respond equally well indicating that at the post-lipolytic level there is no desensitization. Acclimation to cold leads to a large increase in the capacity for nonshivering thermogenesis, and this involves an increased response to injected norepinephrine. During acclimation to cold, there are cellular recruitments both of mitochondria in general and of thermogenin specifically.
