Eugenia López

Biochemical and Mitochondrial Changes Induced by Cd, Fe and Zn in Limnodrillus hoffmeisteri

Se estudio el efecto de las concentraciones subletales de Cd (0,64 µg/L), Fe (0,043 mg/L) y Zn (0,31 mg/L) en forma aislada y en mezcla sobre la actividad de la succinato deshidrogenasa (SD) y la fosfatasa alcalina (AP) en las mitocondrias de las celulas epiteliales del tracto digestivo en el oligoqueto Limnodrillus hoffmeisteri despues de 96 h de exposicion en sedimentos artificiales. La SD se inhibio significativamente, particularmente en los tratamientos con Cd en forma aislada (92,57%), mientras que la AP se incremento con Cd en forma aislada (73,23%). Sin embargo, cuando este metal se mezclo con Fe y Zn, la inhibicion de la SD fue menor (67,82%) que con Cd en forma aislada, lo que mostro un efecto antagonistico y la AP incremento su actividad (73,23%). Sin embargo, cuando este metal estaba en mezcla con Fe y Zn, la inhibicion de la SD fue menor (67,82%) que con Cd en forma aislada, mostrando un efecto antagonistico y un incremento en la actividad de la AP (73,26%). Las mitocondrias fueron danadas estructuralmente por exposicion al Cd en forma aislada. Sin embargo, con los metales en mezcla, los efectos toxicos pudieron ejercer efectos interactivos provocando un menor dano estructural en la mitocondria de las celulas del epitelio del tracto digestivo que cuando el Cd estaba en forma aislada.

Cadmium, iron, and zinc uptake individually and as a mixture by Limnodrillus hoffmeisteri and impact on adenosine triphosphate content

Heavy metals, such as Fe, Zn, and Cd, are major pollutants in aquatic ecosystems. These toxicants usually are present in these ecosystems in the form of mixtures, and their effect on exposed organisms is the result of interactions occurring between the metals as well as with other pollutants and environmental factors. The present study evaluated the uptake of Cd, Fe, and Zn individually and as a mixture and their effect on adenosine triphosphate (ATP) content in Limnodrillus hoffmeisteri, an important aquatic organism given its resistance to large amounts of these xenobiotics. Test organisms were exposed for 96 h to sediment treated with each of these metals individually and as a mixture. The metal concentrations used were equivalent to the zero lethal concentration of these pollutants as determined in a previous study. At the end of the exposure period, metal concentration in medium and organism as well as ATP content in the latter were quantified. Metal uptake was measured by determining the bioconcentration factor at 96 h. All three metals elicited an important decrease in ATP content when acting singly and as part of a mixture. When present as a mixture, their uptake and effect on L. hoffmeisteri are modified. Therefore, a joint-action toxicity approach should be used for toxicity evaluations involving these pollutants.

Toxicity and Uptake of Zinc in the Planarian Dugesia dorotocephala in Natural Sediments

ABSTRACT Zinc uptake and protein, hemocianine, and metallothionein concentrations were studied in Dugesia dorotocephala exposed to Zn-spiked natural sediments in a recirculation system. Exposures to Zn ranged from 0.129 to 4.43 mg Zn/kg of sediment. Metallothionein and protein concentrations increased after treatment with Zn; however, the hemocianine concentration decreased. Metallothionein production could be an effective defense mechanism in planaria. The 96-h EC50 for Zn against D. dorotocephala was 12.52 mg Zn/kg of sediment.