Oil Blue N or Na as a Fat Stain for Animal Histology

Oil blue N or NA gives precise dark blue staining of fatty substances in animal tissues when supersaturated solutions in dilute isopropanol are used. A stock saturated solution in 60% isopropanol, when diluted to 40 or 50% isopropanol, gives good staining in 5 to 10 minutes, without appreciable precipitate.Suitable counterstains are 1:1000 solutions of Janus green B, Bismarck brown Y and Bismarck brown R. These require about 5 minutes and should be followed by one-minute differentiation in 5% acetic acid. Of the three, Bismarck brown R gives the best contrast.