Using frozen sections from human muscle biopsies, we assessed the value of Nile blue and Nile red, two fluorescent probes, as stains for lipid droplets in normal and pathological skeletal muscle fibers. In normal muscle, lipid storage disorders, and mitochondrial myopathies, Nile blue stained the lipid droplets as yellow-gold fluorescent structures. The lipid droplets were also seen as yellow-gold fluorescent structures in Nile red-stained sections, but the outstanding feature in these preparations was the staining of the membrane network of the muscle fibers and membrane proliferations in pathological muscle as red-orange fluorescent structures. These results suggest that both Nile blue and Nile red stains are useful for visualization of lipid droplets and membrane proliferations in pathological muscle biopsies.
