Staining of intestinal goblet cells with ruthenium red in semithin sections

For a correlative light and electron microscopy of intestinal goblet cells, postembedding staining with ruthenium red (RR) was performed in epoxy-embedded sections. Tissue blocks were fixed in buffered aldehyde and embedded in a mixture of Quetol 651, nonenyl succinic anhydride (NSA), methyl nadic anhydride (MNA), and DMP-30. Sections at 0.4-0.5 micron in thickness were mounted on grids and were treated with an aqueous solution of RR followed by osmium tetroxide, uranyl acetate and lead citrate. Postembedding staining of epoxy sections revealed the interaction between RR and anionic groups by both light and electron microscopy. Light and electron microscopic observation of identical sites in semithin sections was successful for the correlations of colored reaction with electron density.