2017 Volume 8 Issue 3 Pages 123-134
Lithium is widely used as materials of such as batteries for small size electronic equipment and electric vehicles, or as ingredients of drugs for manic-depressive psychosis. As the toxic influence of lithium on organism would be weak compared with other metals, lithium is not necessarily noted as toxic substance. However, the amount of lithium released into environmental is predicted to increase in future. That is why estimation of the toxicity of lithium will be important. In this study, we examined the toxic effect of lithium chloride on medaka. We found that LC50 of lithium ion on medaka larvae was 18.2 mg/L. Furthermore, we found that sodium chloride and sodium dihydrogenphosphate increased LC50 of lithium ion to 97.9 mg/L and 164 mg/L, receptivity, suggesting that these salts reduced the toxicity of lithium chloride remarkably. Such effect of coexisting salt was observed also in toxicity test using adult fish. Expression pattern analyses of oxidative stress marker genes suggested that exposure to lithium chloride enhances the expressions of SOD genes, but coexisting sodium dihydrogenphosphate diminishes the expressions of them. From these results, it was suggested that lithium chloride introduced the oxidative stress in medaka, and the coexisting sodium dihydrogenphosphate reduces such stress, as well as lowers mortality induced by exposure to lithium chloride.