Toxicological, cellular and gene expression responses in earthworms exposed to copper and cadmium

This study correlates sub-organismal changes with toxicological effects in earthworms (Lumbricus rubellus) exposed to copper and cadmium. Both metals reduced survival and reproduction at the highest concentration (LC50 5.11 μM Cu g-1 and 4.04 μM Cd g-1; cocoon production EC50s 5.17 μM Cu g-1 and 1.86 μM Cd g-1, all values as dry mass soil). Cadmium significantly reduced lysosomal membrane stability (at 1.86 μM Cd g-1 and higher), upregulated metallothionein gene expression (at least sevenfold in all treatments) and reduced lysosome-associated-glycoprotein gene expression. Copper did not lower lysosomal membrane stability, but did upregulate metallothionein gene expression (at 2.5 μM Cu g-1), reduce lysosome-associated-glycoprotein gene expression and gave a nonlinear pattern for mitochondrial ribosomal subunit transcript expression (reduced at 0.35 and 0.811 μM Cu g-1; higher at 2.5 μM Cu g-1). Correlation of metal body residue concentrations and cellular and molecular genetic responses with juvenile production rate confirmed a relationship for metallothionein expression, lysosomal membrane stability and cadmium tissue concentration in cadmium-exposed worms. Relationships between responses were also found for both metals. These suggested mechanisms for the interaction of cadmium and copper with specific gene products and with organelle (mitochondrial, lysosomal) functioning. [Copyright &y& Elsevier]