THE EFFECTS OF GADOLINIUM ON XENOPUS LAEVIS EMBRYONIC DEVELOPMENT

Lanthanides are present everywhere on the earth’s crust with relatively wide concentration ranges and a toxicity considered low. Gadolinium (Gd) is one of the most widespread; it is used in technological devices and in contrast media for diagnostic imaging. Its concentration in the rivers of industrialized, densely populated areas is often anomalous; in Germany, for example, it is up to three orders of magnitude higher than the expected natural values1. Many aquatic organisms are vulnerable to lanthanides2. Few studies have analyzed their potential long-term effects infreshwater. We used Xenopus laevis as a model system and the FETAX assay3,4, the expression of genes involved in early embryonic development and the ROS production to evaluate the possible toxic effects of Gd. We also verified whether it could activatethe multixenobiotic resistance mechanisms (MXMR) and induce an immune response. The embryos were exposed to Gd ions ranging from 0.2μg/L to 80μg/L considering the environmental concentrations. The FETAX assay showed that Gd is not lethal to Xenopus embryos; between 40 and 80μg/L, the treated embryos reach longer lengths than the controls and at 40μg/L 15% are malformed. As concentration increases, embryos show tachycardia and total ROS production increases. Finally, Gd modifies the expression of early embryonic genes, stimulates the production of cytokines at highest concentrations and activates the MXMR pump at the lowest. These data indicate that Gd, although not lethal for embryos, modifies their growth and exerts a slight toxic/teratogenic effect; it also induces tachycardia and activates the immune response. The observed phenotypic modifications are ascribable to modifications in the expression of genes responsible for the “construction” of the tadpole. This may be due to the production of ROS, which is known to affect gene expression, but also to the difficulty of embryos to activate MXMR. However, the most interesting results are visible at the highest concentrations used.