Localization of mercury in CNS of the rat. V. Inhalation exposure to metallic mercury.

The autometallographical technique has been used to determine the distribution and cellular localization of mercury deposits in the Wistar rat CNS after exposure to elemental mercury vapor (50-550 micrograms Hg/m3 of air for 4-24 h). In animals exposed to 50 micrograms Hg/m3 for 8 h, silver-enhanced mercury grains were confined to the capillary walls. Increasing the concentration of mercury to 500 micrograms Hg/m3 caused mercury staining to appear in neurons in the corpus striatum, mesencephalic nucleus of the trigeminal nerve and cerebellar deep nuclei. In the spinal cord, mercury appeared primarily in the motoneurons of lamina IX. Following exposure to 550 micrograms Hg/m3 for 12 h mercury was additionally detected in the ependyma. Animal exposure to 550 micrograms Hg/m3 for 24 h resulted in visible mercury deposits in the cerebellar and cerebral cortices. In the cerebral cortex, mercury was present in neurons populating lamina III in the isocortex. No mercury was detected in the allocortex. In the cerebellar cortex, mercury staining was limited to the Purkinje cells. Neurons in the thalamus contained heavy accumulations of mercury. Heavy staining for mercury was detected in lung alveolar macrophages in sections prepared from animals exposed to 550 micrograms Hg/m3 for 24 h. In animals exposed to 500 micrograms Hg/m3 or more, the primary target cells were the neurons, but glia cells also contained scattered mercury deposits. Ultrastructurally, mercury deposits were detected in the lysosomes.