Evidence for the presence of brown adipose tissue in the pig.

Small quantities of tissue closely resembling brown adipose tissue have been found in pigs aged two to three months. The tissue, which was taken post mortem from near the great veins in the neck, in the subscapular area and close to the adrenal and thyroid glands, was embedded in connective tissue or white adipose tissue. Examination under the light microscope and electron microscope revealed the following features characteristic of brown adipocytes: multilocular fat: large, round nucleus; numerous mitochondria with cristae; the presence of large amounts of glycogen, and the close proximity of numerous unmyelinated nerve cells with synaptic vesicle filled varicosities. No mitochondrial inclusions were seen. It is suggested that this finding of brown adipose tissue could lead to a better understanding of the control of non-shivering thermogenesis.