Free radical and brain aging : role of metallothionein in the aging of Beagle dog I

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Beagle dogs showed a variety of morphological age-related brain changes including neurona dystrophic axonal changes, astrogliosis and amyloidosis characterized by the formation of s plaques in the cerebral cortex. To study the roles of metallothioneins (MTs) in the brain, the expression pattern of metallothioneins in the brain of aged Beagle dogs was examined. Inter MT-I & -II immunoreactivity as well as signals for MT-I & -II mRNA were shown in the hypertrophic astrocytes in the brains with severe age-related changes. These MT-I & -II positive astrocytes dominated in the thalamus, cerebral cortex and medulla, where remarkal age-related changes including iron and lipofucin deposition were observed. In contrast, MT-I II expression was considerably weak in the brains of dogs with mild age-related changes. On other hand, both MT-III immunoreactivity and signals for MT-III mRNA were demonstrated in neurons in the brain regardless of the intensity of the age-related changes.