The periodic acid Schiff reaction (PAS) is used to demonstrate the presence of 1-2-glycols, and is consequently an important method in the histochemistry of carbohydrates and the histological demonstration of many structures.
Solutions Periodic acid (0.5% aqueous specified). Schiff's reagent (Coleman’s specified). Harris’ hemalum Light green working solution (0.2% aqueous Light Green diluted 1:5 with distilled water)
Ammonia water (water with 3 drops concentrated ammonia per 100 mL)
6µ paraffin sections of neutral buffered formalin fixed tissue are suitable.
Other fixatives are likely to be satisfactory, although glutaraldehyde should be avoided.
Bring sections to distilled water via xylene and ethanol.
Digest using a diastase, hyaluronidase, or sialidase procedure.
Oxidize in Periodic Acid for 5 minutes
Rinse in distilled water
Place in Coleman’s or another Schiff's Reagent for 15 minutes.
Wash in running water for 10 minutes to develop the pink color.
Counterstain with one of the following:–
Harris’ hematoxylin for 6 minutes, then
Wash in running water and transfer to 1% acid ethanol for 3-10 quick dips.
Transfer to 1% acid ethanol for 3-10 quick dips.
Wash in distilled water
Dip in ammonia water to blue the sections.
Wash in running water for ten minutes.
Light green working solution for 10 seconds.
Dehydrate with ethanol, clear with xylene and coverslip using a resinous medium.
1-2-glycols – red
Nuclei – blue
Background – green (if light green used)
Light Green is better used when delineation of fungi is required.
Tap water and ammonia decolorize Light Green, so proceed directly to dehydration.
Glutaraldehyde fixed tissues will have a non-specific positive background staining.
This must be blocked before step 2.
Reference McManus, J. F. A., (1946)
Stain Technology, v23, p99.