Functional Development in Brown Adipose Tissue

Abstract

Brown adipose tissue is prominent in newborn and young mammals including man and our experimental animal — the rabbit. It has two important functions. Firstly, it is a store and supply of fatty acids, and secondly, it is a site of extra heat production during cold exposure. Structurally the tissue is formed of a single cell type surrounded by a rich capillary network. The relationship between the size of any organ and its functional capacity is bound to be complex, however, in view of the relatively simple structure of brown adipose tissue it seems probable that there is a close and direct relationship between the tissue’s weight and its capacity to produce heat or release fatty acids. It is therefore of interest that the size of brown adipose tissue relative to body weight in rabbits reaches a maximum about the time of birth. In absolute terms it continues to increase in size to maturity (fig. I). This observation alone suggests that brown adipose tissue has a special function in the newborn period. We have been interested in the factors determining its function and development.