Toluidine blue Stain

Mast cells are found in the connective tissue and their cytoplasm contains granules (metachromatic) composed of heparin and histamine. Toluidine blue should stain mast cells red-purple (metachromatic staining) and the background blue (orthochromatic staining). Metachromasia, tissue elements staining a different color from the dye solution, is due to the pH, dye concentration and temperature of the basic dye. Blue or violet dyes will show a red color shift, and red dyes will show a yellow color shift with metachromatic tissue elements.

Fixation: 10% Formalin.

 Sections: paraffin sections at 5 um.

​Result:
Mast cells --------------------------- violet/red purple.
Background ------------------------- blue.  



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