Metabolic activity of brown adipose tissue in T3-treated hamsters

Triiodothyronine (T3) treatment induced marked hypertrophy of the brown adipose tissue (BAT), similar to that observed in cold-acclimated animals, although partly due to fat deposition. Similar to cold acclimation, T3 treatment also increased the oxidation of succinate by tissue slices without concomitant increase in isolated mitochondria. It is therefore suggested that thyroid hormones, like cold acclimation, effect conformational changes in the mitochondria, leading to greater expression of the succinic oxidase in the tissue. T3 treatment was not followed by any change in the respiratory activity of tissue slices in the presence of alpha-GP. Likewise, no change was found either in other oxidative activities tested in isolated mitochondria (e.g., NADH and cytochrome oxidases) or in the concentration of the components of the electron transport chain in the mitochondria.