Which fixative is the fixative of choice for glycogen?

• A. Ethyl alcohol
• B. Formalin
• C. Glutaraldehyde
• D. Osmium tetroxide

Answer: (A)

Glycogen is a water-soluble carbohydrate, so preserving it during fixation requires a method that prevents its leaching out of the tissue. An alcohol-based fixative like ethyl alcohol rapidly dehydrates the tissue and precipitates glycogen, effectively locking it in place rather than dissolving or washing it away. This preserves the glycogen content for later histochemical staining, such as PAS, where intact glycogen is important for accurate visualization. In contrast, aqueous fixatives like formalin can cause glycogen to diffuse out of the tissue, and fixatives like glutaraldehyde or osmium tetroxide are optimized for proteins or lipids rather than preserving glycogen. Therefore, ethyl alcohol is the best choice for preserving glycogen.