Subcellular energy balance of Odontesthes bonariensis exposed to a glyphosate-based herbicide

• basal adenylates, phosphagens and the AEC index of O. bonariensis were determined in some tissues.
• impact on subcellular energy balance of sublethal glyphosate exposure was analyzed.
• chronic exposure of O. bonariensis to glyphosate did not affect brain AEC.
• exposure to the herbicide produced adverse effects on the energy metabolism in liver and muscle.

Water pollution by agrochemicals is currently one of the most critical problems for the conservation of aquatic ecosystems. Glyphosate [N-(phosphonomethyl) glycine); PMG] is the main broad-spectrum post emergence herbicide used for the control of a wide range of pests in soybean crops. Adenylate energy charge (AEC) reflects the energy balance of the cells, a measure of the energy available from the adenylate pool: adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP). Background adenylates, phosphagens and the AEC index of two year old Odontesthes bonariensis were determined in some tissues by HPLC, and the impact on subcellular energy balance of sublethal glyphosate-based herbicide exposure was analyzed. The doses used were 0 (control tank), 1 or 10 mg PMG L−1, trials were carried out during 15 days. AEC values in brain, liver and muscle from control fish were 0.37±0.02, 0.49±0.05 and 0.56±0.03, respectively (means±SEM). While brain ATP concentrations were undetectable (hence low values of AEC), the muscle tissue showed the highest concentrations of the more energetic molecules: 0.18 μmole ATP g−1 and 8 μmole phosphocreatine g−1 (PCr g−1). In the brain, no significant changes were detected in exposed fish compared to controls. Instead, in both the liver and muscle of animals exposed to the highest concentration of the herbicide, significant changes in the AEC (reduction of 26% and 15%, p<0.05) with respect to the control group were determined. Chronic exposure (15 days) of Odontesthes bonariensis to 1 and 10 mg L−1 of formulated glyphosate did not affect brain AEC. However, the highest concentration of the herbicide produced a significant decrease in liver and muscle AEC manifesting adverse sublethal effects on the energy metabolism. These results suggest the usefulness of AEC as a biomarker of fish glyphosate exposure.