Arsenic Toxicity and HSP70 Expression in Xenopus laevis Embryos

Abstract

The evaluation of the effect of trace metals on health can be difficult, because of their presence in the environment in various chemical forms. Exposure to arsenic compounds is an example of this complexity, as it can be present in the environment in inorganic and organic forms. The effects of arsenic in vertebrates are complicated by several variables, such as speciation of the element, the exposure route, and the susceptibility of the particular animal species. The embryotoxicity and teratogenicity of three arsenic species — sodium arsenite (NaAsO₂), disodium hydrogen arsenate (Na₂HAsO₄) and dimethylarsinic acid [(CH₃)₂AsOOH] — were evaluated by the modified frog embryo teratogenic assay on Xenopus (FETAX). We also show how the classical FETAX endpoints, based on morphological and morphometrical analysis, can conveniently be integrated with the study of molecular markers. Possible changes in the expression of the mRNA for the heat-shock protein HSP70, following exposure to NaAsO₂, were examined by using the reverse transcriptase polymerase chain reaction. HSP70 mRNA is strongly induced by arsenic.