Ultrastructural and biochemical characterization of human brown adipose tissue in pheochromocytoma.

The amount and distribution of brown adipose tissue (BAT) in healthy adult human subjects remain uncertain. BAT has been described in patients with pheochromocytoma. This pathological situation was chosen to try to characterize human BAT using both morphological and biochemical criteria. Typical multilocular brown adipocytes were observed; the cytoplasm of these adipocytes was filled with mitochondria with numerous tightly packed cristae, as in rat or hamster BAT. Isolated mitochondria exhibited a loose respiratory coupling sensitive to guanosine diphosphate; the chloride conductance of these mitochondria was reduced by the addition of this nucleotide. It is concluded that in patients with pheochromocytoma, there is a large amount of a tissue around the adrenal glands and kidneys which fullfills the ultrastructural and biochemical criteria for a BAT.