OXYGEN CONSUMPTION OF BROWN ADIPOSE TISSUE IN NORMAL AND HYPOTHYROID MICE

Abstract

The functional relation-ship between thyroid hormone and interscapular brown adipose tissue with respect to cold exposure was studied in the mouse. Cold exposure for 5 days produced a significant increase in fat-free dry matter of interscapular brown adipose tissue in the mouse. Concurrent rise in O2 consumption of this tissue was found, while that of epididymal white fat tissue remained unchanged. Following single injection of thyroxine [T4] both fat-free dry matter and QO2 increased gradually and showed the peak at 96 hr. The effect of norepinephrine on the O2 consumption of brown adipose tissue was rather transient. The stimulatory effect of cold exposure and norepinephrine on the O2 consumption of brown adipose tissue was abolished by methylthiouracil treatment. Administration of T4 into the hypothyroid mice restored the response to norepinephrine. The hypothyroid mice showed a significant hypertrophy of brown adipose tissue when the animals were exposed to cold.