Detection of mercury in rat spinal cord and dorsal root ganglia after exposure to mercury vapor.

Adult male Wistar rats were exposed to mercury vapor, 50 micrograms Hg/m3, 6 hr/day, 5 days/week, over 1-, 2-, 3-, 4-, 6-, and 8-week periods. Sections from the spinal cord and dorsal root ganglia from spinal levels C1, C5, T6, and L1 were stained with the autometallographical technique and the distribution of mercury deposits described at light and electron microscopical levels. A quantitative analysis of the amount of mercury in blocks of the spinal cord was performed using cold vapor atomic absorption spectrophotometry. After an exposure period of 2 weeks, silver-enhanced mercury grains could be observed in spinal cord neurons located in Rexed laminae IV-X. Ventral horn motoneurons were heavily stained in all of the spinal cord segments. Ependymal cells and glial cells of both the spinal gray and white matter contained cytoplasmatic mercury accumulations in rats exposed to mercury vapor for 4 weeks. In the dorsal root ganglia, only ganglion cells showed a faint mercury staining and the amount of staining was notably less than that seen in the ventral horn motoneurons. At the ultrastructural level, mercury was seen primarily within lysosomes of target cells. The quantitative mercury measurements demonstrated that spinal cords from rats exposed to mercury vapor for 6 or 8 weeks contained a significantly higher concentration of mercury than those from control animals.