Effects of chlorpyrifos on acetylcholinesterase activity in two freshwater fish species (Cnesterodon decemmaculatus and Gambusia affinis)

BERNAL-REY, D.; DOS SANTOS AFONSO, M.; MENENDEZ HELMAN R. J.

International Journal of Environment and Health

Inderscience

Año: 2017

1743-4955

Chlorpyrifos (O,O-diethyl O−3,5,6-trichloropyridin-2-yl phosphorothioate, CPF) is a widely used organophosphate insecticide. In the present work the effect of chlorpyrifos exposure on acetylcholinesterase activity (AChE, biomarker of neurotoxicity) was evaluated in two non-target species of freshwater fish (Gambusia affinis and Cnesterodon decemmaculatus). The animals were exposed to sublethal concentrations (1 and 5 µg CPF × L-1) or remained in control water for 96 h. Acute exposure to CPF inhibited AChE activity by 48% and 69% in C. decemmaculatus and by 27% and 36% in G. affinis for 1 and 5 µg CPF × L-1, respectively. Acetylcholinesterase activity appears to be a sensitivity biomarker for CPF exposure in both species, even to CPF low concentrations that are environmentally relevant. C. decemmaculatus has a high susceptibility to CPF compared with G. affinis. In vitro assays showed no differential sensitivity of the enzyme to CPF between G. affinis and C. decemmaculatus. However, the dissimilar behaviour of AChE after in vivo exposure to CPF could be due to the higher sensitivity of AChE of C. decemmaculatus to chlorpyrifos-oxon (CPF-oxon, a product of the natural oxidative desulfuration of CPF). The half maximal (50%) inhibitory concentration (IC50) for in vitro exposure to CPF-oxon were 10.2 nM and 54.2 nM for C. decemmaculatus and G. affinis, respectively, which supports the existence of a different sensitivity of the enzyme between both species.