Differential regulation of metallothionein-I and metallothionein-II mRNA expression in the rat brain following traumatic brain injury

In this study, we investigated the expression of metallothionein (MT)-I and MT-II in the rat brain following traumatic brain injury (TBI). In the early stage, significant induction of MT-I and MT-II were observed in various regions including ventricle walls, pia mater, and dentate gyrus. At 12-24 h after TBI, strong induction of MT-I mRNA was observed in cerebral cortical layer II/III, amygdala, and piriform cortex where neurons reside. On the other hand, MT-II appeared to be expressed mainly in glial cells localized in the cerebral cortex and hippocampal formation. Three days after TBI, MTs were observed in the vimentin-positive astrocytes in the penumbra as revealed by double immunohistochemistry. The differences in expression of MT-I and MT-II in different brain regions and cell types (neuron vs. glial cells) suggests that multiple regulatory mechanisms are involved in the control of MT expression following brain injury.