Effects of chronic treatments upon the brown adipose tissue of young rats. I. Cold exposure and hyperthyroidism

1. The gross composition, triglycerides and phospholipids of brown adipose tissue were studied in young and adult rats chronically treated with cold or thyroxine. 2. Cold induced an increase of the total water, protein and phospholipid of tissue while the main effect of thyroxine treatment was an accumulation of triglycerides. Thyroxine treatment prevented the cold-induced increase of phospholipid percentage in the tissue. 3. Cold exposure altered the fatty acid pattern of phospholipids, whereas thyroxine had smaller and different effects. 4. The differential effects of cold and hyperthyroidism upon triglycerides and phospholipids of brown adipose tissue are briefly discussed.