Metallothionein in the human brain

The localization of metallothionein (MT), a heavy metal binding protein of low molecular weight, in the human brain was investigated by the immunohistochemical technique, and also the amounts of MT were assayed by radioimmunoassay. Immunohistochemically, MT was found in pia mater, ependymal cells, protoplasmic astrocytes and neuropil of the gray matter, and fibrous astrocytes of the white matter of the brain. Cytoplasm, processes and some nuclei of protoplasmic and fibrous astrocytes showed strong MT immunostaining. Vascular feet and adventitia of the blood vessels were also positive for MT immunostaining. With aging, MT deposited thickly in the pia mater and in the dilated perivascular spaces showing reticular appearance, especially in those, so-called etat crible of basal ganglia and centrum semiovale of hypertensive and aged cases. According to the radioimmunoassay, the amount of MT in the brain increased with age.