Figure 2.

Localisation of scavenger receptor class B type I (SR-BI) in large cytoplasmic lipid droplets during fat absorption. (A) Electron micrograph of an Epon section showing numerous lipid droplets in the cytoplasm. Two morphologically distinct types of lipid droplets were seen: some relatively large and dark (*) and some relatively small and light, often seen in clusters (#). (B) Immunogold labelling of an Epon section for SR-BI, showing that only the large and dark lipid droplets were labelled. Note that labelling was not confined to the rim but distributed over the entire droplet. (C) Double immunogold labelling of an ultracryosection for apolipoprotein A-1 (10 nm particles) and SR-BI (5 nm particles) of a cluster of the small and light type of lipid droplets. Apolipoprotein A-1 was localised to the rim of the droplets, thereby identifying them as nascent chylomicrons. SR-BI labelling was not seen in chylomicrons. Bars 2 μm (A); 1 μm (B); 0.2 μm (C).