This technique is used to stain the mucins in tissues. As shown below, the alcian blue reacts with mucins to stain them blue. The mucin reaction is pH dependant; with the normal pH used for staining is pH 2.5 which stains up acid mucins.
This technique can be combined with the PAS to differentiate between acidic and neutral mucins, with the alcian blue staining up the acidic mucins, while PAS stains the neutral mucins. This is valuable as it allows differentiation of the mucin types. It is also important to stain in the correct order, as staining the PAS before the Alcian blue can lead to problems with the staining.
Acid Mucins |
Blue |
Neutral Mucins |
Magenta |
Photo – x10 Alcian Blue PAS staining
This technique is when the Alcian Blue is carried out on its own.
pH2.5 Acid mucins |
Blue |
pH1 Amyloid |
Green |
Nuclei |
Red |
Photo - Alcian Blue in colon x10
The two main types of mucins found in the body are listed in the table below.
Mucin Type |
Structure and Location within the body |
Acid Mucins |
Positively charged and form electrostatic bonds with tissue polyanions bearing either carboxyl or sulphate groups. These are mostly found in the colon. |
Neutral Mucins |
Found in the gastric lining cells in the stomach and in brunner glands of the duodenum. Also present in the alimentary and respiratory tract goblet cells and prostate glands. |
The acid mucins subtypes are listed in the table below.
Acid mucin sub division |
Location in the body |
Strongly sulphanated |
Found in connective tissue and epithelial, these can be found in skin, cartilage, bone, blood vessels and umbilical cord. They will react at highly acidic pH 0.5. |
Weakly suphanated |
Epithelial tissue, normally found in colon goblet cells. They stain up with cationic dyes at pH 1 |
Carboxylated - sialomucin |
There are two forms one is an enzyme labile which are digested by the enzyme sialidase, commonly found in bronchial, submucus glands, submandibular salivary glands and goblet cells in the small intestine. While the enzyme resistant form are epithelial in origin and are found in colon goblet cells. |
Hyaluronic Acid |
This is found in connective tissue in the umbilical cord and is also an important constituent of the synovial fluid. This has a reactive site on the carboxyl group and stains up at pH 2.5. |
Sulphanated Sialomucins |
These react with sulphanated mucins and are extracted by the enzyme sialidase and have been found in tumours of the prostate |