Uso de biomarcadores para avaliação dos efeitos agudos da exposição de herbicida comercial em peixe neotropical, Piaractus Brachypomus

Abstract

Herbicides are agricultural pesticides directed at weeds control, considered the most frequent pesticides in Brazilian fresh waters. The 2,4-D + picloram-based herbicides are among the widely used formulations, which might promote contamination of aquatic environments. This study evaluated the toxicological potential of commercial herbicide 2,4-D + picloram-based (Norton®) Piaractus brachypomus using multi-biomarkers. Median-lethal concentration (LC50-96h) was determined and neurotoxic, cytogenotoxic, hematological, biochemical and morphological biomarkers were used to evaluate the effects of the compound in different tissues. The results showed that the determined LC50-96h was 1.54 g L-1 and the behavioral disorders presented include loss of reflex, muscle spasms and opercular hyperventilation. The juveniles were exposed to a sublethal concentration of 1.11 g L-1 in a static system for 96 hours and the observed effects showed the inhibition of acetylcholinesterase in the muscle, indicating a disturbance in the neuromuscular system. The haematological examinations indicated macrocytic anemia, probably a compensatory response to maintain adequate oxygen transport. There was no increase in micronuclei frequency, however, the exposure promoted an increase in nuclear anomalies, suggesting cytogenotoxic effects. The hepatotoxicity biomarkers showed inhibition of alkaline phosphatase activity, indicating that exposure may have caused changes in the hepatocyte membrane. Liver morphology exhibited pathologies, such as architecture and cellular alteration, atrophy and nuclear alterations. Changes in metabolic intermediates, in rate of plasma glucose and muscle glycogen, showed dysfunction in carbohydrate metabolism. Lesions in the gills included constriction of the pillar cell system and hypertrophy of the lamellar epithelium, demonstrating physiological adjustments to preserve the functions, of which they maintained the excretory function. In the kidneys, individual morphological lesions were observed, such as architecture and cellular alteration, capable of causing losses associated with the tubular resorption capacity. The biotransformation system and lipid peroxidation indicate that the herbicide did not impair the detoxification capacity of the antioxidant defense system and there were no elevated effects of oxidative stress. In conclusion, the results showed that the commercial herbicide promoted morphophysiological changes in the tissues in P. brachypomus, demonstrating that the effects can compromise the animal's health.