What is the fixative for enzyme histochemistry on muscle?

• A. Frozen, no fixation
• B. Formalin
• C. Bouin
• D. Zamboni

Answer: (A)

Enzyme histochemistry depends on preserved enzymatic activity within the tissue so the substrate can be converted to a colored product where the enzyme is located. Fixatives such as formalin, Bouin, and Zamboni chemically cross-link proteins, which inactivates enzymes and prevents the histochemical reaction from occurring. To visualize enzyme distribution in muscle, the tissue is kept unfixed and prepared as frozen sections; rapid freezing preserves enzyme activity without cross-linking, allowing the substrate reaction to take place in situ. This is why using frozen tissue with no fixation is the correct approach.