The Role of Metallothionein in Hard Tissue

We studied the metallothionein (MT) induction by cadmium (Cd) in the dental pulp and bone in rats. In order to clarify the cell response to Cd in the hard tissue, the isoform-specific expression of MT mRNAs (MT-I and MT-II) was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) method, and the localization of MT was confirmed by immunohistochemical studies. Both MT-I and MT-II mRNA levels were increased within 3 hours by Cd administration in both the dental pulp and bone. In the dental pulp, MT protein was localized in the specific cell type of odontoblasts (secretory odontoblasts and resting odontoblasts). In the bone, MT-positive cells were time-dependently increased, and the positive cells were mainly localized in osteocytes. The cell-specific induction of MT may be associated with Cd accumulation and Cd-induced the hard tissue injury in vivo.