The Periodic Acid Schiff (PAS) reaction is a histochemical staining technique used to identify carbohydrates, particularly polysaccharides, in tissues. It is named after the reagents used in the reaction: periodic acid and Schiff's reagent.
The reaction begins with the oxidation of the hydroxyl groups in the polysaccharides present in the tissue by periodic acid. This results in the formation of aldehyde groups. The tissue is then treated with Schiff's reagent, which contains a dye known as fuchsin. The aldehyde groups react with the fuchsin dye, forming a colored compound that can be visualized under a microscope.
The PAS reaction is widely used in histology and pathology to identify various substances, including glycogen, mucin, and basement membrane components. It can be performed on frozen or paraffin-embedded tissue sections, making it applicable to a wide range of tissues and organs.
In addition to its use in identifying carbohydrates, the PAS reaction can also be used to detect other substances such as nucleic acids and some proteins, depending on the modifications made to the staining procedure.
The PAS reaction is an important tool in diagnostic pathology, as it allows for the identification and characterization of various substances in tissues. By highlighting specific carbohydrates and other components, it can provide valuable information about the structure and function of tissues, aiding in the diagnosis of various diseases and conditions.
