Cresyl Violet Stains Mast Cells Selectively: Its Application to Counterstaining in Immunohistochemistry

The thiazine dye toluidineblue (TB) is well known to stain mast cellsand hyaline cartilagemetachromatically, and thus is mostly often used for their identification. However, TB is not suitable for counterstainingin immunohistochemistry, because of its high-background stainingin the cytoplasm of other cell species and in extracellular structures. To expand the knowledge about dyestuffs staining mast cellsin consideration with their usage in immunohistochemistry, we determined the stainability of several thiazinesand oxazines, which are structurally related compounds to TB, using sections of mast cell-containing tissues. We found that all azinedyes used metachromatically stained mast cellsand cartilage. Among these dyes, an oxazines cresyl violet(CV) stained mast cellswith lower background, suggesting that those are useful for detecting mast cellsand for counterstainingin immunohistochemistry. To ascertain its utility, CV was used in immunostaining of bHSDs in sections from adult rat ovary. Imm...