[Effect of breeding temperature on the growth and composition of brown fat in the newborn rat].

The weight and the lipid, water and norepinephrine contents of the interscapular brown adipose tissue from 1, 3, 7, 11, 14 and 21 day aged rats were measured. The animals were maintained at an ambiant temperature of 16 degrees, 23 degrees or 28 degrees C from birth. It is concluded that nonshivering thermogenesis is not necessary after 3 days of age in animals kept at 28 degrees C and after 11 days of age in the ones kept at 23 degrees C. However that thermogenesis persists for all the suckling period in those kept at 16 degrees C.