A scanning electron microscopic study on the difference between white and brown adipose tissues in the rat.

Lipid globules in the white and brown adipose tissues in the rat were well preserved with prolonged postfixation in OSO4. The difference between the surface of white adipose tissue and that of brown adipose tissue was observed in such a way that the surface of the brown adipocyte was lumpy owing to the presence of intracellular lipid globules, and that the surface of the white adipocyte was considerably smooth. After the matrix of lipid globules was dissolved during specimen preparation, the subgranules embedded in the matrix were disclosed on the inner surface of the lipid globules. The cut surface of the white adipocyte contained a large lipid droplet and the amount of cytoplasm was poor, whereas the brown adipocyte had several lipid droplets and many small granules in the cytoplasm.