Approved Abstracts

Evaluation of biochemical biomarkers in Nile tilapia (Oreochromis niloticus) exposed to methylphenidate



Author(s): Batalhão IG; Lima D; Boscolo CNP; Silva DGH; Almeida EA;
Presenter: Daína Lima

The wastewater treatment plants (WWTP) are not designed to completely remove pharmaceuticals from effluents, which its final destination is surface water. Methylphenidate (MPH, known as Ritalin) and its metabolite, ritalinic acid, have already been found in the environment at levels of ng.L-1, but there are few studies that report their damage to the ecosystem and non-target organisms. In this work, was evaluated the effects of MPH, in environmental concentrations, in Nile tilapia (Oreochromis niloticus), through the antioxidant defense system, biotransformation enzymes, levels of lipid peroxidation and esterase activity. Male fish were exposed to 0, 20, 100 and 200 ng.L-1 of MPH for 5 days. The activity of biotransformation phase I enzymes 7-ethoxyresorufin-O-deethylase (EROD) and 7-benzyloxyresorufin-O-dealkylase (BROD) did not show statistical difference, both in tilapia liver and gills. Catalase (CAT) activity in gills decreased of 5.03 and 4.60-fold in fish exposed to 100 and 200 ng L-1 of MPH, respectively, compared to control group. The same pattern was observed in glutathione peroxidase (GPx) activity in gills, a decreased of 1.60, 1.63 and 2.41-fold in groups exposed to 20, 100 and 200 ng L-1, respectively, compared to control group. No differences were observed in activity of CAT and GPx in the liver of tilapia after five days of exposure of MPH. The levels of lipid peroxidation in the liver of tilapias exposed to 20, 100 and 200 ng L-1 of MPH were 2.24, 1.75 and 1.68-fold lower, respectively, compared to control group. However, no changes in lipid peroxidation were observed in the gills. The enzymatic activity of acetylcholinesterase (AChE) and carboxylesterase (CbE) in the liver of tilapia showed no statistical differences after exposure to all tested MPH concentration. In contrast, in gills AChE activity was 1.51 and 1.58-fold lower in the 100 and 200 ng L-1 MPH-exposed groups, respectively, compared to the control group. On the other hand, in the groups exposed to 20 and 200 ng L-1 of MPH, the CbE activity in gills was 1.43 and 1.56-fold higher, respectively, related to control group. The results show that the effect of MPH was more expressive in the gills compared to the liver of exposed fish, highlighting the importance of evaluating biomarkers responses in different fish tissues. Also, was evidenced that the MPH could negatively affect the antioxidant capacity of the fish, despite it did not cause an increase in lipid peroxidation. No changes were observed in EROD and BROD activity, indicating that cytochrome P450 isoform 1A (CYP1A) had no effect on the MPH biotransformation at the concentrations tested. On the other hand, the increase in CbE activity in gills suggests an effort by the organisms to metabolize MPH. This data corroborates the fact that the gills were more responsive than the liver to exposure to MPH, and could explain the absence of biochemical changes in the liver. It is possible that the increase in CbE, and thus its consequent metabolization, have decreased the bioavailability of MPH to the liver, protecting this organ against possible negative effects of this drug.

Keywords: antioxidant enzymes; biotransformation enzymes; ecotoxicology

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