RESUMO
The aim of this work was to assess the effects of 1 week copper exposure (6.2, 108, 210 and 414microM) on Scenedesmus vacuolatus and Chlorella kessleri. The strains showed different susceptibility to copper. Copper content was determined in both strains by total X-ray reflection fluorescence analysis (TXRF). In S. vacuolatus, the increase of medium copper concentration induced an augmentation of protein and MDA content, and a significant decrease in the chlorophyll a/chlorophyll b ratio. S. vacuolatus showed a significant increase of catalase activity in 210 and 414microM of copper, and a significant increment of SOD activity and GSH content only in 414microM of copper. On the contrary, C. kessleri did not show significant differences in these parameters between 6.2 and 108microM of copper. Increased copper in the environment evokes oxidative stress and an increase in the antioxidant defenses of S. vacuolatus.
Assuntos
Antioxidantes/metabolismo , Chlorella/metabolismo , Cobre/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Scenedesmus/metabolismo , Proteínas de Algas/biossíntese , Catalase/biossíntese , Quelantes/análise , Quelantes/metabolismo , Chlorella/efeitos dos fármacos , Chlorella/crescimento & desenvolvimento , Clorofila/biossíntese , Cobre/análise , Cobre/metabolismo , Ácido Edético/análise , Ácido Edético/metabolismo , Glutationa/biossíntese , Peroxidação de Lipídeos/efeitos dos fármacos , Malondialdeído/análise , Malondialdeído/metabolismo , Modelos Estatísticos , Oxirredução , Scenedesmus/efeitos dos fármacos , Scenedesmus/crescimento & desenvolvimento , Espectrometria por Raios X , Superóxido Dismutase/biossínteseRESUMO
We analyzed the dietary copper effects in the estuarine crab Neohelice (Chasmagnathus) granulata and its interaction with water salinity. Crabs were maintained at 2 per thousand and 30 per thousand salinity for 5 weeks and they were fed with commercial food supplemented with the green alga Scenedesmus vacuolatus previously exposed to copper. No mortalities were observed, but crabs maintained at 2 per thousand salinity accumulated on average 40% more copper compared to animals maintained at 30 per thousand salinity. At 2 per thousand salinity, superoxide dismutase (SOD) activity and reduced glutathione (GSH) levels were increased at the first and second weeks, respectively, while lipid peroxidation and protein oxidation were evident after 4 weeks of copper exposure. At 30 per thousand salinity, all measured variables increased progressively but were significantly higher only at the end of the assay (5th week), except for protein oxidation that remained unchanged throughout the experiment. The hepatosomatic index (HSI) was significantly decreased in response to copper exposure, but only in crabs acclimated to 2 per thousand. These findings have suggested that dietary copper exposure induces greater metal accumulation and larger oxidative stress responses in crabs maintained at 2 per thousand salinity.