Sex Difference in Expression of Metallothionein mRNA in Mouse Liver after Low Dose Cadmium Injection

Abstract

Environmental pollution caused by cadmium (Cd) has been an object of public concern for considerable time. Among heavy metals, both Cd and mercury are well known to be severe toxic to living tissue. Interestingly, it has been suggested that there are sex differences in Cd effects1-4). For example, blood pressure in male rats was elevated by administration of Cd, but not in females2). Itai-Itai disease, that has been considered a chronic symptom of Cd poisoning, was reported in old women, especially5). However, there is no consensus whether Cd effects are more severe in males or females, so a sex difference in the effect of Cd has remained obscure. Since Margoshes, et al.6) reported that low molecular weight proteins from horse kidney cortex contained abundant Cd and Kagi, et al.7) identified these proteins as metallothionein (MT), there have been many discussions concerning the functions of MT. According to reports suggesting that MT is induced in animal tissues by Cd administration and noting a positive correlation between dose-dependent increases in hepatic MT and Cd LD50, the detoxification of heavy metal has been considered one of the main functions of MT8). Therefore, an investigation of differences in MT synthesis by Cd in male and female animals should be of considerable interest for evaluating sex differences in the influences of Cd. In this study, we investigated MT mRNA expressions in the livers of male and female mice after Cd injections using the RT-PCR method.