ADVERSE EFFECTS OF CADMIUM AND ALUMINUM ON ZEBRAFISH DEVELOPMENT

Exposure to several metals during pregnancy has been shown to be harmful to the developing fetus.1,2 The use of zebrafish embryos and larvae is always more widespread and accepted in the scientific community for the screening of dangerous effects exercised by pollutant.3 Zebrafish embryos at shield stage4 were separately exposed to different concentrations of aluminum chloride (AlCl3) and cadmium chloride (CdCl2) for 48 h with the purpose to assess the toxic actions of these metals on their development. After 24 and 48 h we carried out phenotypic and lethality analysis. We observed a greater toxic action of CdCl2 on these stages of development. In fact at 24 and 48 h of exposure the total lethality (LC100) was observed at 1 and 0.5 mM for cadmium respectively and at 40 and 25 mM for aluminum. The phenotypic analysis doesn’t show alterations induced by AlCl3 while the embryos exposed to CdCl2 showed pericardial oedema, hypopigmentation, alterations in the development of the tail and of the body axis. Considering the minor effects of AlCl3 we carried out toxicity tests on larval stage, a system commonly recognized as more susceptible to pollutants toxicity.5 Larvae at protruding mouth stage4 were exposed to different concentration of AlCl3 for 48 h and in these experiments we observed a LC100 of 0.25 and 0.20 mM respectively after 24 and 48 h of exposure. These values were comparable to those obtained with CdCl2. We observed the ability of AlCl3 to induce heart alterations with pericardial oedema and a reduction in heart rate after exposure to 50 and 100 μM. Cytotoxic effects of these metals were also observed on the nervous system in embryos and in larvae. We find an increase of apoptotic index in embryos exposed to 9 μM of CdCl2 for 24 h while in larvae exposed for 48 h to 100 μM of AlCl3 there was a reduction in number of GFAP-positive cells. These data show that CdCl2 is more toxic than AlCl3 on zebrafish development, both are neurotoxic, but AlCl3 has also cardiotoxic ability.