Exposure to different glyphosate formulations on the oxidative and histological status of Rhamdia quelen

Due to the wide use of glyphosate (GLY) in soybean cultivation, their residues in the environment may affect non-target organisms such as fish, developing toxic effects. Despite GLY being widely used in Brazil, there are few studies comparing the effects of commercial formulations in native freshwater fish species. Silver catfish (Rhamdia quelen) were exposed to three different commercial formulations of GLY 48 % (Orium(A (R)), Original(A (R)) and Biocarb(A (R))) at 0.0, 2.5 and 5.0 mg/L for 96 h. The effects in thiobarbituric acid-reactive substances (TBARS), catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST) and histological alterations were analysed in the liver, whereas alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were studied in the plasma. In the liver, TBARS levels increased and CAT decreased in all treatments and herbicides tested in comparison with the control group. The SOD increased at 2.5 mg/L of Orium(A (R)), Original(A (R)) and 5.0 mg/L Orium(A (R)) and Biocarb(A (R)), whereas GST increased at 2.5 mg/L Orium(A (R)) and decreased at 2.5 mg/L Biocarb(A (R)) when compared to the control group. The main histopathological alterations in hepatic tissue were vacuolisation, leucocyte infiltration, degeneration of cytoplasm and melanomacrophage in all GLY treatments. The ALT decreased after exposure to 2.5 mg/L of Biocarb(A (R)) and AST increased at 2.5 mg/L of Orium(A (R)), Original(A (R)) and 5.0 mg/L of Biocarb(A (R)) in comparison with the control group. In summary, the oxidative damage generated by GLY may have caused the increased formation of free radicals that led to the histological alterations observed in hepatocytes.