PAS Staining Protocol for Frozen Sections

PAS staining protocol for frozen sections post we have briefly explained about PAS staining method’s principle, requirements, PAS staining protocol, and result with label.

PAS Staining Protocol for Frozen Sections

PAS Staining Protocol for Frozen Sections can detect glycogen within tissues such as the liver, the cardiac, and the skeletal muscle on formalin-fixed paraffin-embedded tissue sections. PAS staining protocol can be used to detect glycogen in frozen sections too. The glycogen, mucin, and fungi will be coloured purple, and the nuclei will be stained blue in PAS staining protocol.


PAS stain in a PAS staining protocol is a histochemical reaction. The periodic acid oxidizes the carbon to carbon bond-forming aldehydes that react to the fuchsin-sulfurous acid that forms the magenta colour.


0.5% Periodic Acid Solution

Periodic acid: 0.5 g

Distilled water: 100 ml

Schiff Reagent

Test for Schiff reagent: Pour 10 ml of 37% formalin into a watch glass. To this, add a few drops of the Schiff reagent to be tested. A suitable Schiff reagent will rapidly turn a red-purple color. A deteriorating Schiff reagent will give a delayed reaction, and the color produced will be a deep blue-purple.

PAS staining protocol

1. Place slides in the movable gray slide holder

2. Counterstain in Hematoxylin (staining line) for 1 minute

3. Rinse well in distilled water by holding a finger over slides, pouring water into the sink, and adding water.

4. Do this 5 times.

5. Quickly dip slides into “Bluing” agent (0.5% ammonium hydroxide)

6. Rinse 1 minute in distilled water until pink color is visible

7. Dehydrate through graded alcohols, 10 short dips in each: 95%, 95%, 100%, 100%

8. Fix in 2 rounds of xylenes, 1 minute in the hood.

9. Coverslip slides.


PAS Staining Protocol for Frozen Sections

Image Source:

Glycogen, mucin and some basement membranes: red/purple

Fungi: red/purple

Background: blue

Positive control

For staining fungus; use a known positive such as those used for the GMS. Use skin, aorta, or normal liver for positive PAS staining.

Further Readings