Distribution of inhaled mercury (203Hg) in various organs

Mercury and its derivatives have long been known to be toxic for the brain and other organs in both animals and man. The distribution of inhaled radioactive mercury (203Hg) in body tissues of rats and mice was investigated by means of a micro-autoradiographic technique. Animals were exposed to 203Hg vapours 6 h daily for 10 days, and then sacrificed at different times after the last exposure. Whole-body autoradiograms showed significant uptake of labelled mercury by the kidney, brain, myocardium, intestine and liver, in decreasing order. Micro-autoradiography demonstrated selective localization of 203Hg in the cytoplasm and processes of neurons, whereas little radioactivity was found in the glial cells of the gray and white matter. High levels of 203Hg were detected in nuclei of the cerebellum, midbrain, pons and medulla, in the Purkinje cells of the cerebellar cortex, and in the epithelium of the ependyma and choroid plexus. In the lung, radioactivity appeared to be confined to the erythrocytes of small blood vessels, which may be the carriers of this metal to the brain. In the liver, ingested but not inhaled radioactivity was concentrated in the reticulo-endothelium. In the kidney, proximal and distal convoluted tubules, but not the medulla or the glomeruli, took up large amounts of inhaled 203Hg. Mercury is distributed to many organs in addition to the brain. It may be transported by circulating red blood cells and it concentrates in the cytoplasm of parenchymal cells.