After hyaluronidase digestion, which mucin type continues to be demonstrated with Alcian blue 1.0?

• A. Glycoproteins
• B. Hyaluronic acid
• C. Chondroitin sulfate A
• D. Sulfated mucosubstances

Answer: (A)

Alcian blue at an acidic pH stains acidic mucins by binding to charged groups on them. When tissue is pretreated with hyaluronidase, the hyaluronic acid component—an acid mucopolysaccharide that is not a glycoprotein—gets digested away. What remains detectable with Alcian blue 1.0 are mucin components that are not hyaluronic acid but still carry charged carbohydrate residues. The mucin type that persists under this pretreatment is the glycoprotein mucins, whose protein core with carbohydrate side chains includes sulfate or carboxyl groups that Alcian blue can bind to at pH 1.0. Hyaluronic acid would no longer be demonstrated because it was digested, and while sulfated mucosubstances can also bind the dye, the question targets the mucin form that remains specifically as a glycoprotein after enzymatic digestion. This illustrates how enzymatic pretreatment helps distinguish mucin types based on their biochemical composition.