Localization of mercury in CNS of the rat. II. Intraperitoneal injection of methylmercuric chloride (CH3HgCl) and mercuric chloride (HgCl2).

The autometallographic method has been used to determine the precise localization of mercury in the brain and spinal cord of adult Wistar rats which had been treated with repeated ip injections of methylmercuric chloride (CH3HgCl; 0.2 to 10.0 mg) or mercuric chloride (HgCl2; 0.2 to 10.0 mg). The distribution of mercury was uneven following administration of HgCl2, while it was fairly homogeneous following CH3HgCl. With both compounds, however, heavy deposits of mercury were present in the motor nuclei of rhombencephalon. In contrast, cerebellar Purkinje cells, Golgi cells, and Golgi epithelial cells only contained mercury in sections from rats exposed to CH3HgCl. In cerebral sections from rats exposed to CH3HgCl, staining intensity in cortical cells varied among the layers, being greatest in laminae III, V, and VI. On the other hand, sections from rats exposed to HgCl2 showed only staining in scattered cells of lamina VI. Following administration of either compound, mercury was detected in the gray matter of the spinal cord mercury. Particularly large deposits were present in the anterior horn motoneurons. At the cellular level, the heaviest staining intensity was seen in neurons, although the cytoplasm of glia and ependymal cells also showed significant deposits in sections from rats exposed to CH3HgCl. In HgCl2-treated rats, the largest accumulations of mercury were seen in the neurons. The ependymal cells were stained to a lesser extent, while glia were devoid of mercury. Ultrastructurally, mercury deposits were located exclusively in lysosomes. The present results demonstrate that the pattern of mercury distribution and its staining intensity in individual cells in the rat CNS are dependent upon the chemical structure of the compound and the duration of its administration.