Brain acetylcholinesterase as an in vitro detector of organophosphorus and carbamate insecticides in water

Abstract

An inexpensive but accurate enzymatic method is proposed for the detection of carbamate and organophosphorus pesticides contaminating water supplies. The method uses an acetylcholinesterase preparation obtained after extraction of rat brain microsomal fraction with Triton X-100. The method is based on inhibition of acetylcholinesterase in the presence of the pesticides. Some phosphorothionate insecticides (e.g. parathion, malathion), which are not direct acetylcholinesterase inhibitors, can also be activated by preincubation with the enzyme preparation. Enzyme assay is performed by a potentiometric method based on the formation of acetic acid in the incubation mixture. Interference of any eventual buffering capacity of the sample can be easily corrected. Malathion, parathion, diazinon and deoxicarbamate inhibited the enzyme at least 20% when they were added to the medium in the limit concentration recommended for public water supplies (0.1 mg/l). The method was evaluated in samples collected from selected locations of Paraiba do Sul river, Rio de Janeiro, Brazil, and it proved to be sufficiently practical and accurate as an alarm routine test for such pesticide classes.