Bouin solution is a good fixative for tissue to be stained with the Fuelgen reaction.

• A. True
• B. False
• C. It is the best fixative for all stains
• D. It is used for stains on frozen sections

Answer: (B)

Feulgen staining detects DNA by first hydrolyzing it with acid to form aldehyde groups, which then react with Schiff’s reagent to give a magenta color. For this to work reliably, the DNA must be well preserved and not masked or lost by the fixative. Bouin solution, with its picric acid and acetic acid components, can interfere with DNA preservation and extraction during processing, and its strong acidic/cross-linking environment can mask DNA sites or remove nucleic acids needed for the Schiff reaction. Because of these effects, Bouin-fixed tissue does not provide the consistent, specific DNA staining that Feulgen requires. In contrast, alcohol-based fixatives like Carnoy’s or 70% ethanol better preserve DNA for Feulgen staining.