Fasting for 36-48 h or food restriction (30% reduction of daily food intake for 6 weeks) caused brown adipose tissue (BAT)
atrophy in hamsters. Fasting-induced
atrophy was characterized by reductions in tissue mass,
DNA,
protein, and
thermogenin. By contrast, food restriction had no effect on tissue cellularity (
DNA) but markedly reduced the tissue
protein and
thermogenin contents. The concentration of
thermogenin in isolated mitochondria was unchanged by fasting or food restriction. Dystrophic hamsters had a reduced BAT mass when compared with weight-matched control hamsters. This resulted from a reduction in tissue cellularity since BAT
DNA,
protein and
thermogenin contents were all reduced. The extent of binding of [3H]
guanosine diphosphate to isolated mitochondria and their content of
thermogenin were similar in normal and dystrophic hamsters. In response to cold exposure, as in normal hamsters, BAT of dystrophic hamsters grew and the tissue
thermogenin increased, but the mitochondrial concentration of
thermogenin did not change. In response to fasting, in contrast with normal hamsters, there was no significant reduction in BAT
DNA in dystrophic animals and the loss of tissue
protein was reduced. However, the relative changes in BAT composition during chronic food restriction were similar in normal and dystrophic animals. Thus, reduction in hamster BAT thermogenic capacity during food deprivation may occur by loss of cells and (or)reduction in the tissue
protein and
thermogenin contents. The extent of
protein and (or)
DNA loss may be dependent upon the original tissue mass and the severity of food deprivation.