Time-dependent distribution of 203Hg-methylmercuric chloride in tissues and cells of rats

The time-dependent distribution of 203Hg-methylmercuric chloride has been studied in the tissue cells of rats by means of microautoradiographic examination and in the liver cells by means of electron autoradiography. Furthermore, the radioactivity of 203Hg in the various organs was measured at the same time. A possible way was suggested to prove that methylmercury might enter the brain through the choroid plexus-cerebrospinal fluid-brain barrier as well as through the blood-brain barrier. Silver grains were selectively localized on the macrophages and glial cells in the paraventricular sites adjacent to the ventricles, subsequently in the submeningeal sites of brain cortex, and also localized on the macrophages and glial cells in the molecular and Purkinje cell layers near the fourth ventricle. Following administration, silver grains rapidly increased in the liver and kidney and then showed a relatively variable decrease. The density of grains was the most concentrated in the endothelium in the liver. A conspicuously large amount of radio activity was noted in the lumen of tubules at the earlier stages and later was found in the epithelial cytoplasm of the proximal and distal tubules in kidney. Radioactivity was remarkable in the blood and certain organs compared to that present in the cerebrum and cerebellum. The damaged cells in the brain, liver, kidney and muscle were not always related to the amount of mercury. There may be some differences between the intoxicity of organic mercury to the cells and sensitivity of the nerve cells themselves to organic mercury.