Surgical denervation of the five sympathetic nerves supplying one lobe of the interscapular brown fat of control rats caused small reductions in mass, protein content and the activity of the thermogenic mitochondrial proton conductance pathway (assessed from guanosine-5'-diphosphate (GDP) binding) when compared to the intact lobe. Denervation did not affect the acute 100% increase in mitochondrial GDP binding capacity seen after a single injection of noradrenaline. Cold-adaptation (4 degrees C for 7 days) or over-feeding (cafeteria diet for 10 days) caused marked increases in the mass, protein content and specific mitochondrial GDP binding in intact brown adipose tissue, but these changes were totally prevented by surgical denervation. These data indicate that the hypertrophy and the increased thermogenic capacity of brown fat induced by cold-adaptation or hyperphagia depend entirely upon the sympathetic innervation of the tissue.
Adaptation, Physiological Adipose Tissue, Brown