John Wiley & Sons, Ltd.

Cholinesterase activity of muscle tissue from freshwater fishes: Characterization and sensitivity analysis to the methyl‐paraoxon organophosphate

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The biochemical characterization of cholinesterases (ChE) from different teleost species has been a critical step ensuring proper use of ChE activity levels as biomarkers on environmental monitoring programs. In the present study, ChE from Oreochromis niloticus, Piaractus mesopotamicus, Leporinus macrocephalus and Prochilodus lineatus were biochemically characterized by specific substrates and inhibitors. Moreover, muscle tissues ChE sensitivity to methyl‐paraoxon (MP) organophosphate (OP) pesticide was evaluated by determining the inhibition kinetic constants (IKC) for progressive irreversible inhibition from muscle ChE by MP, as well as, the IC50 for 30 min for each species. Our results have indicated that acetylcholinesterase (AChE) must be present in the muscle from P. mesopotamicus, L. macrocephalus and P. lineatus; and O. niloticus possesses an atypical cholinesterase or AChE and butyrylcholinesterase (BChE). Furthermore, there is a large difference regarding the sensitivity of these enzymes to MP. The determined IC50 values for 30 min were: 70 nM (O. niloticus), 258 nM (P. lineatus), 319 nM (L. macrocephalus) and 1,578 nM (P. mesopotamicus). Our results have also indicated that the use of efficient methods for extracting these enzymes, their kinetic characterization and determination of sensitivity differences between AChE and BChE to organophosphate compounds, are essential for precision ChE activity levels reported in environmental monitoring program interpretation. Environ Toxicol Chem © 2014 SETAC

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