Which fixative is necessary for the preservation of chromaffin granules?

• A. Primary chromate fixative
• B. 70% alcohol
• C. 10% neutral buffered formalin
• D. Zenker solution

Answer: (A)

Chromaffin granules contain catecholamines that are easily leached out or degraded during routine processing. They stay in place only when a fixative containing chromium is used, because chromium forms stable complexes with the granule contents and effectively traps the catecholamines inside. This preserves the characteristic dark pigment produced by the chromaffin reaction, allowing the granules to be demonstrated later. Other fixatives, like alcohol or standard formalin, don’t provide that chromium-based stabilization, so the granules can diffuse or be lost during processing. Zenker solution has chromium but is harsher; the key idea is that chromium-containing fixation is needed to preserve these granules, making the primary chromate fixative the best choice.