Cadmium and copper display different responses towards oxidative stress in the kidney of the sea bass Dicentrarchus labrax

Copper and cadmium were i.p. injected into the fish Dicentrarchus labrax. Cu as Cd-treated fish showed an enlargement of the lysosomal membrane of the kidney (pronephros), Cu being more toxic than Cd. Following injection, metal uptake, measured in muscle, liver and kidney, was much higher with cadmium treatment than with copper, the kidney being the main accumulating organ of cadmium in which metal accumulation is correlated with increased zinc level, suggesting metallothionein induction. In vivo exposure to metal decreases the lysosomal membrane stability of pronephros with a half dose of 127 ng g(-1) Cu and 735 ng g(-1) Cd. Lipid peroxidation, expressed as malondialdehyde equivalents (MDA), and catalase activity were measured in kidney subcellular fractions. When added in vitro, Cu significantly raises the MDA level (365% at 200 mu M), Cd having a lower effect (20% at 500 mu M) Catalase activity is significantly reduced by Cd whereas Cu does not produce any significant effect at the tested concentrations. Results suggest that although both metals cause in vivo damage to pronephros lysosomal membrane, Cu activates the redox process generating oxyradicals but does not affect in vitro the protective catalase activity unlike Cd which appears to weakly participate in oxyradical generation but alters in vitro protective catalase activity. (C) 2000 Elsevier Science B.V. All rights reserved.