[Effects of adaptation temperature on the development of brown adipose tissue in the rat]

Male Long Evans rats were acclimated to 28 degrees C, 5 degrees C or to a daily fluctuating temperature (Cy group). The development of brown adipose tissue (BAT) was compared to that of controls maintained at 22 degrees C. Acclimation to 28 degrees C did not affect the BAT weight. After 10 days of cold exposure, the total BAT weight was increased in the 5 degrees C group, but not in the Cy group compared to controls. After four months the BAT weight was increased by about 130% in 5 degrees C group and only by 60% in Cy. In both groups the increase of abdominal BAT was four times larger than the interscapular one. No histological difference was observed between interscapular and abdominal BAT of cold acclimated rats : the size of lipid droplets is smaller than in controls. The physiological significance of the important cold induced hypertrophy of abdominal BAT is discussed.