Argentaffin substances have what key property in silver-based histochemical procedures?

• A. Bind to silver solution and reduce it to metallic form
• B. Stain fats blue
• C. Fix tissue by cross-linking proteins
• D. Dehydrate tissue

Answer: (A)

Argentaffin substances have the ability to reduce silver ions to metallic silver on the tissue itself. In silver-based histochemical procedures, these substances bind to the silver solution and donate electrons, converting Ag+ to Ag0 and forming a visible metallic silver deposit. This happens without any external reducing agent, which is why they’re described as argentaffin. The resulting dark precipitate marks the presence of these substances, such as in neuroendocrine or APUD-type granules. The other options describe general processing steps or staining properties not specific to argentaffin behavior.