Renal expression of metallothionein in rats treated with cadmium.

Background. The intrarenal localization of metallothionein (MT) expression has not been studied in detail. Therefore, we investigated the effects of acute exposure to cadmium on the renal expression of MT. Methods. MT mRNA expression was estimated quantitatively at 2, 6, 24, and 72 h after the injection of cadmium (1 mg/kg) to the intraperitoneum of male Sprague-Dawley rats. The site of cadmium-induced MT mRNA expression was determined, by the reverse transcription polymerase chain reaction (RT-PCR), using microdissected tubules. Immunoblotting and immunohistochemistry were also performed, to determine the localization of MT protein. Results. The mRNAs of MT-I and MT-II were significantly upregulated at 2 h and peaked at 24 and 6 h, respectively. RT-PCR revealed the expression of cadmium-induced MT mRNA mainly in the proximal tubules. Immunoblotting detected a clear 14-kDa band corresponding to MT protein, and immunohistochemistry showed abundant MT protein in the renal cortices of cadmium-treated rats. Conclusions. Our findings suggest that the proximal tubules are responsible for the cadmium-induced renal expression of MT mRNA and protein. [ABSTRACT FROM AUTHOR]