In vitro and in vivo inhibition of Gammarus pulex acetylcholinesterase by diazinon

Abstract

This study was designed to investigate the effect of the in vivo and in vitro exposure to the organophosphorothioate pesticide diazinon, its metabolite diazinon oxon and diazinon in a commercial formulation on the AChE activity of the freshwater amphipod Gammarus pulex. Only diazinon oxon at concentrations of ≥ 50x103 nM oxon caused a significant inhibition of acetylcholinesterase (AChE) activity in vitro. However, diazinon oxon had no significant impact on the enzyme activity following in vivo exposure. The latter mode of exposure to either ≥ 10 nM of diazinon or ≥ 5 nM of the diazinon in the commercial formulation caused a significant reduction in AChE activity of treated organisms. This study supports the finding of previous studies that suggested AChE activity in aquatic animals as a valuable biomarker of diazinon.