A Simple Colloidal Silver Method (Autometallographic Technique) for Demonstrating Inorganic Mercury in Brain Sections

Abstract

Standard methods for mercury measurement estimate total mercury burden in tissues but are not informative about cellular localization, for which histochemical techniques are needed. Because the main target of the toxic effects of mercury is the nervous system, it is of particular interest to localize its reservoir within the brain. This paper presents a simple, autometallographic method for demonstrating inorganic mercury in paraffin sections of brain by utilizing a buffered colloidal silver solution that contains hydroquinone. Formalin fixed, paraffin processed brain sections are cut at 7 μm and hydrated with deionized water. The sections are placed in a buffered colloidal silver nitrate solution containing hydroquinone and kept in a 37°C oven for 18 to 20 min. They are then washed immediately in hot running water and rinsed in deionized water. Following treatment with 2% sodium thiosulfate for 1 min, they are rinsed in deionized water and counterstained with nuclear fast red for 3 min or with cresyl violet acetate for 5 min. After the slides are rinsed in deionized water, they are dehydrated in alcohol, cleared in xylene, and mounted with synthetic resin. Mercury stains black and the results are consistent and reliable. (The J Histotechnol 23:337, 2000)

Keywords:

• formalin fixation
• histochemistry
• methylmercury
• silver nitrate
• total mercury burden