Diet as a confounding factor in the toxicity of the insecticide endosulfan in the freshwater fish Australoheros facetus

CRUPKIN, AC; ITURBURU, FG; CHISARI, AN; MENONE, ML

Portland- Oregon

Congreso; SETAC North America 31st Annual Meeting.; 2010

SETAC

A limitation of most of the biological effect measurements is that biomarker data interpretation must always be carefully controlled for false-negative and false-positive results, since the effects of non-pollution-related confounding factors may interfere with biomarker responses. The goal of this work was to evaluate the effect of diet -if any- on the following biomarkers: glutathione-S-transferases (GST), glutathione reductase (GR), catalase (CAT) and malondialdehide (MDA) in liver of Australoheros facetus exposed to the insecticide endosulfan. Fishes were acclimated during 20 days with isocaloric diets containing 50 and 10% protein, diet 1 and 2 respectively. They were exposed to: 0 (control), 0.5 and 10 ug/L endosulfan during 24 h. Factorial ANOVA (factors: diet and treatment) with interaction and principal effects models was used. In controls the activity of GST and CAT was significantly lower (p<0.05) in fishes fed with diet 2 than in fishes fed with diet 1. Fishes fed with diet 2, exposed to 0.5 ug/L endosulfan showed increased CAT activity and higher MDA content with respect to their controls (p<0.05). At 10 ug/L, the activity of CAT was similar to control values while MDA increased 2-folds respect to control. Fishes fed with diet 1 showed inhibition of CAT and GST at 10 ug/L endosulfan. These results demonstrate that the pesticide exerts oxidative stress in the organism. On the other hand, interaction between diet/treatment was observed for GST, CAT and MDA. For example, fishes exposed to 10 ug/L endosulfan showed inhibition of CAT when fed with diet 1 while the activity was significantly increased in fishes fed with diet 2.  GR showed no interaction (diet-treatment), nor effects of diet and treatment. The effect of endosulfan resulted influenced by the diet in A. facetus, denoting the importance of considering this factor to interpret the toxicity of environmental pollutants in bioassays as well as in field studies.