Induction of metallothionein mRNA expression in the mouse liver after cadmium injection as measured by the reverse transcriptasepolymerase chain reaction method

Metallothioneins (MTs) are low molecular weight proteins that have been considered to be important metal-binding proteins in the defense against cadmium (Cd) toxicity in animals. These proteins are known to be induced by the injection of heavy metals such as Cd. Previously, we developed the RT-PCR method to measure the level of MT mRNA expression. In this study, we analyzed the time course and dose response of Cd-induced MT-I mRNA expression in the male and female mouse liver. By this method, we measured hepatic MT-I mRNA expression which reached the highest peak 6 h after subcutaneous injection of 1.1 mg/kg Cd in 9-week old male and female mice compared with those of corresponding controls (0 h). There was no statistical difference in the hepatic MT-I mRNA expression between male and female mice 6 h after the injection of this dosage. However, it is notable that the MT-I mRNA expression in male mice was much higher than that in females 6 h after injection of 0.5 mg/kg Cd. Thus, the induction of hepatic MT-I mRNA expression is dependent on the sex of the mouse, the dosage and the time course of Cd.