Acetylcholinesterase enzyme activity in carp brain and muscle after acute exposure to diafuran

Abstract

Sublethal adverse effects may result from exposure of aquatic organisms to insecticides at environmentally relevant concentrations. Fingerlings of the common carp (Cyprinus carpio, Linnaeus, 1758), grass carp (Ctenopharyngodon idella, Valenciennes, 1844), and bighead carp (Aristichthys nobilis, Richardson, 1845) were exposed to diafuran, an insecticide widely used during rice cultivation in Southern Brazil. The aim of this study was to verify the relationship between the lethal concentration (LC 50 ) of diafuran and the acetylcholinesterase (AChE) activity in brain and muscle tissues of these species as a possible early biomarker of exposure to this insecticide. LC 50 was determined for fish exposed to diafuran concentrations during 96 h (short term): common carp: control, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 mg L -1 ; grass carp: control, 1.0, 2.0, 3.0 and 3.5 mg L -1 and, bighead carp: control, 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0 mg L -1 , as well as the determination of AChE at concentrations near LC 50 for these species. LC 50 values (nominal concentrations) were 1.81 mg L -1 for the common carp, 2.71 mg L -1 for the grass carp and, 2.37 mg L -1 for the bighead carp. All carps exposed to diafuran were lethargic (lower concentrations) or immobile. Diafuran inhibited the acetylcholinesterase activity in brain (~38%) and muscle (~50%) of all species. Muscle of bighead carp under control treatment showed higher specific AChE activity than brain (14.44 against 5.94 mmol min -1 g protein -1 , respectively). Concentrations of diafuran used for rice cropping may affect Cyprinus carpio, Ctenopharyngodon idella and Aristichthys nobilis behaviors and the AChE activities in brain and muscle of these species may be an early biomarker of toxicity of this insecticide. Key words: Cyprinus carpio, Ctenopharyngodon idella, Aristichthys nobilis, pesticide, lethal concentration ATIVIDADE DA ENZIMA ACETILCOLINESTERASE EM CÉREBRO E MÚSCULO DE CARPAS APÓS EXPOSIÇÃO AGUDA AO DIAFURANRESUMO: Exposição a inseticidas em concentrações elevadas no ambiente podem ocasionar efeitos adversos subletais em organismos aquáticos. Alevinos de carpa húngara (Cyprinus carpio, Linnaeus, 1758), carpa capim (Ctenopharyngodon idella, Valenciennes, 1844) e carpa cabeça grande (Aristichthys nobilis, Richardson, 1845) foram expostos ao diafuran, um inseticida utilizado na cultura do arroz no sul do Brasil. O objetivo deste estudo foi verificar a relação entre concentração letal mediana (CL 50 ) do diafuran e a atividade da enzima acetilcolinesterase (AChE) em cérebro e músculo dessas espécies, como um possível biomarcador inicial da exposição a este inseticida. A CL 50 foi determinada com peixes expostos a concentrações de diafuran em 96 h: carpa húngara: controle; 0,5; 1,0; 1,5; 2,0; 2,5 e 3,0 mg L -1 ; carpa capim: controle; 1,0; 2,0; 3,0 e 3,5 mg L -1 e carpa cabeça grande: controle; 0,5; 1,0; 1,5; 2,0; 3,0 e 4,0 mg L -1 , bem como a determinação da AChE em concentrações próximas da CL 50 para essas espécies. (5,5'dithio-bis 2 nitrobenzoic acid), bo...

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