Jpn. J. Pharmacol. 86 (1), 65-72 (2001)

Localization of Metallothionein (MT) and Expression of MT Isoforms Induced by Cadmium in Rat Dental Pulp

Chiharu Aoki Sogawa1,*, Norio Sogawa1, Toshio Yamamoto2, Nariaki Oda1, Tetsuyoshi Inoue3, Kenji Onodera1 and Hiroaki Furuta1

1Department of Dental Pharmacology, 2Department of Oral Anatomy I, 3Department of Oral Microbiology, Okayama University Dental School, 2-5-1 Shikata-cho, Okayama 700-8525, Japan

*Corresponding author. FAX: +81-86-235-6664, E-mail:

Abstract: We investigated the induction of metallothionein (MT) by cadmium (Cd) in the dental pulp of rat incisors. Time-course studies of MT mRNA expression after single Cd injection were observed by Northern-blot analysis. The isoform-specific expressions of MT mRNAs (MT-I, MT-II and MT-III) were observed using the reverse transcriptase-polymerase chain reaction (RT-PCR) method. Both MT-I and MT-II mRNA levels increased within 3 h, peaked at 3 h and then decreased. These findings demonstrated that MT-I and MT-II mRNA were rapidly induced by Cd in dental pulp. MT-III mRNA was constitutively expressed in rat dental pulp, but the expression level did not change by Cd treatment. The localization of MT protein in Cd-treated rat dental pulp was determined by immunohistochemical staining using anti-MT antibody against MT-I and MT-II. MT protein was localized in the specific cell type of odontoblasts (secretory odontoblasts and resting odontoblasts). In conclusion, it is likely that stained MT in the immunohistochemical study should be MT-I and/or MT-II. Furthermore, MT-I and/or MT-II in Cd-treated rat dental pulp was localized in odontoblasts, in which accumulation of Cd were reported. The cell-specific synthesis of MT may be associated with its metal storage and detoxification role in dental tissues.

Keywords: Metallothionein, Cadmium, Dental pulp, Odontoblast, Pulp cell
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