TY - JOUR

T1 - A comparative study of acetylcholinesterase and general-esterase activity assays using different substrates, in vitro and in vivo exposures and model organisms

AU - Cao, Yi

AU - Herrero-Nogareda, Laia

AU - Cedergreen, Nina

PY - 2020/2

Y1 - 2020/2

N2 - Acetylcholinesterase (AChE) and general-esterase (GE) activities are important to understand detoxification processes of xenobiotics. The assays to quantify them have employed different substrates, inhibitors, types of experiments (in vitro and in vivo) and model organisms. The aim of this work was to give a systematic overview of the effect of the above factors on the outcome of AChE and GE activity measurements. We showed that AChE activity could be measured with the substrate acetylthiocholine iodide (AChI) but not with acetylcholine bromide (AChB) and only in in vitro assays. For GE activity, Michaelis-Menten kinetics differed between the substrates 4-methylumbellifery butyrate (4-MUB) and 1-naphtyl acetate (1-NA) in the measurements of in vitro activity, but their inhibition curves and IC50 values for the general inhibitor tetraisopropyl pyrophosphoramide (iso-OMPA) were similar, confirming that both substrates targeted the same group of enzymes. The GE substrate 4-MUB was applicable both in vitro and in vivo, while 1-NA was only applicable in vitro due to its high acute toxicity. When comparing the zooplankton crustacean Daphnia magna and the sediment dwelling Chironomus riparius, the latter had a four-fold higher maximal AChE activity (Vmax) and a higher susceptibility to the AChE inhibitor BW284c51 (four-fold lower 50% inhibitory concentration, IC50), but a lower maximal GE activity and lower susceptibility to iso-OMPA (higher IC50), indicating significant species differences between in C. riparius and D. magna. We conclude that both choice of substrate and exposure method matters for the outcome of esterase assays and that esterase compositions between species may vary significantly.

AB - Acetylcholinesterase (AChE) and general-esterase (GE) activities are important to understand detoxification processes of xenobiotics. The assays to quantify them have employed different substrates, inhibitors, types of experiments (in vitro and in vivo) and model organisms. The aim of this work was to give a systematic overview of the effect of the above factors on the outcome of AChE and GE activity measurements. We showed that AChE activity could be measured with the substrate acetylthiocholine iodide (AChI) but not with acetylcholine bromide (AChB) and only in in vitro assays. For GE activity, Michaelis-Menten kinetics differed between the substrates 4-methylumbellifery butyrate (4-MUB) and 1-naphtyl acetate (1-NA) in the measurements of in vitro activity, but their inhibition curves and IC50 values for the general inhibitor tetraisopropyl pyrophosphoramide (iso-OMPA) were similar, confirming that both substrates targeted the same group of enzymes. The GE substrate 4-MUB was applicable both in vitro and in vivo, while 1-NA was only applicable in vitro due to its high acute toxicity. When comparing the zooplankton crustacean Daphnia magna and the sediment dwelling Chironomus riparius, the latter had a four-fold higher maximal AChE activity (Vmax) and a higher susceptibility to the AChE inhibitor BW284c51 (four-fold lower 50% inhibitory concentration, IC50), but a lower maximal GE activity and lower susceptibility to iso-OMPA (higher IC50), indicating significant species differences between in C. riparius and D. magna. We conclude that both choice of substrate and exposure method matters for the outcome of esterase assays and that esterase compositions between species may vary significantly.

KW - Chironomus riparius

KW - Daphnia magna

KW - Enzyme activity

KW - Esterase

KW - In vitro

KW - In vivo

U2 - 10.1016/j.ecoenv.2019.109954

DO - 10.1016/j.ecoenv.2019.109954

M3 - Journal article

C2 - 31759743

AN - SCOPUS:85077344959

VL - 189

SP - 1

EP - 10

JO - Ecotoxicology and Environmental Safety

JF - Ecotoxicology and Environmental Safety

SN - 0147-6513

M1 - 109954

ER -