Another technique that would look almost identical to the technique shown is which?

• A. Schmorl technique for reducing substances
• B. PAS
• C. Alcian blue pH 2.5
• D. Prussian blue

Answer: (C)

Alcian blue stains acidic mucins by binding to the negatively charged glycosaminoglycans; the pH of the stain dictates which mucins are targeted. At pH 2.5, both sulfated and carboxylated mucins are stained blue, producing a pattern that is very similar to what you’d see with Alcian blue at a different but nearby pH. In tissues where the mucin composition doesn’t strongly differentiate between sulfated and carboxylated types, the blue staining from Alcian blue at pH 2.5 will look almost identical to the same stain at another pH value. The other techniques shown detect entirely different substances or produce different color reactions (reducing substances with Schmorl’s method, neutral carbohydrates with PAS, iron with Prussian blue), so they wouldn’t resemble the Alcian blue mucin staining.