Autometallographic detection of mercury in rat spinal cord after treatment with organic mercury.

Autometallography was used to localize mercury in rat spinal cord after intraperitoneal administration of methylmercuric chloride (200 micrograms CH3HgCl daily). The technique permits small amounts of mercury sulfides and mercury selenides to be visualized by silver-enhancement. Mercury deposits were observed by light microscopy only in neurons. In all of the spinal cord segments selected (first cervical segment, C1; fifth cervical segment, C5; sixth thoracic segment, T6; and first lumbar segment, L1) the mercury was observed with cumulative dosages of 6000 micrograms CH3HgCl and greater. Laminae VII, VIII, and IX contained the majority of stained neurons, whereas laminae IV, V, VI, and X had a relatively lower density of mercury-containing neurons. Stained neurons were confined to specific cell groups, such as Clarke's column, nucleus intermedio-lateralis, nucleus cervicalis centralis, and nucleus dorsomedialis. At the ultrastructural level, mercury deposits were restricted to lysosomes of neurons and occasional accumulations in the lysosomes of ependymal cells.