Toluidine blue stain


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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.

1) Deparaffinize and hydrate sections to distilled water.
2) Stain sections in toluidine blue working solution for 2-3 minutes.
3) Wash in distilled water, 3 changes.
4) Dehydrate quickly through 95% and 2 changes of 100% alcohol (10 dips each since stain fades quickly in alcohol).
5) Clear in xylene or xylene substitute, 2 changes, 3 minutes each.
6) Coverslip with resinous mounting medium.

Mast cells --------------------------- violet/red purple.
Background ------------------------- blue.