What is the purpose of Alcian blue staining in this protocol?

• A. To differentiate epithelial from connective tissue mucins
• B. To stain nuclei
• C. To identify lipids
• D. To detect proteins

Answer: (A)

Alcian blue staining highlights acidic mucins by binding to their sulfated and carboxylated glycosaminoglycans, turning these mucins blue. This makes it possible to distinguish mucins produced by epithelial cells (such as goblet cells) from those in the connective tissue matrix, because acidic epithelial mucins will stain blue while non-acidic components do not. So the stain’s purpose in this protocol is to differentiate epithelial mucins from connective tissue mucins. Note that Alcian blue is not used for nuclei, lipids, or general protein detection.