Genotoxicidade e alterações na capacidade antioxidante em tilápia do nilo (Oreochromis niloticus) exposta ao herbicida hexazinona

Abstract

Population growth demands a higher food production, which to achieve greater success and avoid the presence of pests leads to a greater use of herbicides that may be able to reach the water table through leaching in the soil causing damage to the aquatic population. A widely used herbicide is hexazinone (HZN) (C12H20N4O2) from the chemical group triazinone, classified as moderately toxic. This herbicide has reached water bodies and can cause great impact on the environment. One way to measure this impact is to use an environmental bioindicator, such as fish. Nile tilapia (Oreochromis niloticus) (Linnaeus, 1758) is one of the most cultivated and consumed fish in Brazil and worldwide. It is a rustic animal, resistant to diseases and high density, being a good experimental animal because it adapts very well to the captivity.The objective of this work was to investigate whether the hexazinone herbicide induces genotoxicity and to alter the antioxidant capacity of the gills of O. niloticus fish. For this, 108 animals were used in total, divided into six treatments with three replicates each. Each replicate contained six animals per aquarium that were exposed for 96 h at concentrations: control 0.0 mg / L, HZN1 8.8 mg / L, HZN2 17.6 mg / L, HZN3 35.2 mg / L, HZN4 70, 4 mg / L and HZN5 140.8 mg / L. After 96 hours the fish were anesthetized and blood and gills were removed. The blood was used to perform the micronucleus tests. The gills were used for the analysis of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and lipid peroxidation product through malonaldehyde (MDA) levels. Fish exposed to concentrations of 17.6 up to 140.8 mg/L showed high frequency of micronucleated erythrocytes. The enzyme superoxide dismutase (SOD) showed lower activity in the animals of the groups exposed to the concentration of 140.8 mg/l, and the enzymes CAT and GST, increased in 17.6 and 17.6 to 140.8 mg/l, respectively. There was no difference in the lipid peroxidation. The results suggest that the herbicide is capable of causing genotoxicity in O. niloticus evidenced by the micronucleus test. The decrease in the activity of the enzyme SOD indicates stress and excessive production of reactive oxygen species (EROS). The increased GST enzyme indicates cellular protection against lipid peroxidation. The hexazinone herbicide can cause DNA damage and oxidative stress in the gills of Nile tilápia.