LOCALIZATION OF METALLOTHIONEIN IN AGED HUMAN BRAIN

The localization of metallothionein (MT), a small molecular weight hea vy metal binding protein in aged human brain, was investigated by immu nohistochemical techniques. The amount of MT and heavy metals (Zn, Cu) were also assayed by radioimmunoassay and atomic absorption spectroph otometry, respectively. Immunohistochemically, MT was found in the pia mater, ependymal cells, protoplasmic astrocytes nand glial processes neuropil of the gray matter and fibrous astrocytes of the white matter of the telencephalon, whereas oligodendroglia and microglia did not s how any positive immunostaining for MT. Cytoplasm, glial processes and some nuclei of protoplasmic and fibrous astrocytes showed strong MT i mmunostaining. Vascular feet and adventitia were also positive for MT immunostaining. Moreover, the pia mater, astrocytes and ependyma in th e diencephalon, mesencephalon, pons, medulla oblongata and spinal cord showed the same positive immunostaining for MT as the telencephalon. In the cerebellum, Bergmann's glia, protoplasmic astrocytes of the gra nular layer and fibrous astrocytes of the white matter showed strongly positive immunostaining for MT. According to the radioimmunoassay, th e amount of MT in the brain was relatively high at about 39.3 +/- 9.5 mug/g wet weight; of the heavy metals in the brain, zinc and copper we re detected.