Efeitos da exposição crônica por herbicida à base de glifosato em peixe Poecilia reticulata (Peter, 1859), com enfâse em mortalidade e marcadores bioquímicos

Abstract

Used worldwide, glyphosate is an organophosphate from the chemical group of modified glycines, characterized by being a broad-spectrum herbicide, with indication of low toxicity for animals. However, there are controversies regarding the safety of its use due to several studies that demonstrate interference in enzymatic activities, antioxidant defense, nervous system, endocrine system, embryotoxic, cytotoxic, histopathological, carcinogenic and reproductive disorders effects. This herbicide works by blocking the shikimate pathway by inhibiting EPSPS, resulting in reduced plant development. The action of glyphosate associated with low toxicity for humans and animals is associated with the fact that the shikimate and aromatic amino acid biosynthesis pathway is plant-specific and has specific characteristics. The effects of the commercial product ROUNDUP® WG were evaluated in two chronic exposure trials of Poecilia reticulata fish and respective control groups. The first test lasted 46 days, using a concentration of 7 mg/L of the product, not being possible to carry out biochemical analyzes due to the high mortality of the animals. The second chronic trial lasted 82 days, with animals exposed to 1.5 mg/L of the product and fish in a control environment. Biochemical markers were used to evaluate parameters of oxidative stress and enzyme activity. After exposure to glyphosate, the samples were collected, respectively liver and muscle from the animals for analysis, using: oxidative stress marker (cellular damage - lipid peroxidation - LPO), antioxidant defense enzyme (glutathione s transferase - GST), enzyme marker of xenobiotic and neurotoxic biotransformation (cholinesterase) and amino acid metabolism marker (glutamate dehydrogenase – GLDH). In fish subjected to contamination of 7 mg/L of ROUNDUP® WG, 90% of animal mortality was observed in 46 days. In the second trial, with fish submitted to 1.5 mg/L of the product, 32.14% mortality was observed in 82 days and no changes were identified in the activities of antioxidant defense enzymes (GST), xenobiotic biotransformation and neurotoxicity ( cholinesterase), amino acid metabolism markers (GLDH) and there was also no indication of damage related to oxidative stress (LPO marker) in the liver and muscle of the animals.