Figure 5.

Signs of browning in rpWAT at the cellular level after 3 and 45 days of cold acclimation

A, multiloculation of lipid droplets and the appearance of the paucilocular adipocytes in rpWAT after 3 days of cold exposure. The majority of adipocytes exhibited paucilocular lipid organization (one dominant lipid droplet), but some individual polygonal cells contained multilocular lipid droplets after 45-day cold acclimation. Scale bars = 20 μm. B, enlargement of the area of rpWAT from rats exposed to cold for 45 days (indicated by an arrow). A large number of mitochondria are evident in all rpWAT adipocytes after 45 days of cold acclimation, whereas a clear gradation in the number and size of mitochondria is evident among neighbouring adipocytes of different morphology: (1) unilocular; (2) paucilocular and (3) multilocular. Multilocular adipocytes (3) are characterized by the largest and most densely packed mitochondria. Insets: enlargement of the framed areas showing differences in mitochondrial size. Magnification 100×, oil immersion.