Which stains are used to demonstrate sulfated sialomucins?

• A. Alcian Blue pH 1.0 and 2.5
• B. Alcian Blue pH 2.5 only
• C. PAS
• D. Congo Red

Answer: (A)

The staining approach hinges on how Alcian Blue binds to acidic mucins at different pH values. At very low pH (1.0), only sulfated mucins remain negatively charged enough to bind Alcian Blue, so sulfated mucins show up. At pH 2.5, Alcian Blue stains all acidic mucins, including both sulfated and carboxylated (sialomucin) groups. By applying Alcian Blue at both pH 1.0 and pH 2.5, you can identify sulfated mucins (they stain at both pH levels) and distinguish them from non-sulfated acidic mucins. This is why using Alcian Blue at both pH values is the method to demonstrate sulfated sialomucins. PAS, Congo Red, and single pH 2.5 staining don’t specifically isolate sulfated mucins.