QUANTITATIVE ASPECTS OF BROWN ADIPOSE TISSUE THERMOGENESIS DURING AROUSAL FROM HIBERNATION

¹ Department of Anatomy, Harvard Medical School, Boston, Massachusetts 02115
² Department of Biological Chemistry, Harvard Medical School, Boston, Massachusetts 02115

The in vitro respiratory rates of brown adipose, heart, and liver tissues were studied in the bat (Eptesicus fuscus) to determine their contribution to the heat necessary for arousal from hibernation. The mean oxygen consumption of the whole animal for arousal from hibernation was 66.2 ml. of which 5.7% is estimated to be utilized by brown adipose tissue, and 1.2% by heart and liver combined. The maximum respiratory rate of brown adipose tissue when stimulated by epinephrine was 134 µl. O₂/l00 mg. fresh tissue/hr. Despite this high in vitro respiratory rate, it seems inadequate, on the basis of other evidence, to account for the heat production expected for brown adipose tissue during arousal from hibernation. A thermogram of a bat arousing from hibernation is presented which provides pictorial evidence of the large thermogenic capacity of brown adipose tissue. It is concluded that the conditions necessary to measure the maximum respiratory rate of brown adipose tissue, such as it occurs during arousal from hibernation, have not yet been achieved.