Cholinesterase activity during embryonic development in the blood-feeding bug Triatoma patagonica

Evaluation of 2,6-dichlorophenolindophenol acetate as a substrate for acetylcholinesterase activity assay

Ellman's method is a standard protocol for the determination of cholinesterases activity. Though the method is ready for laboratory purposes, it has some drawbacks as well. In the current article, 2,6-dichloroindophenol acetate is performed as a chromogenic substrate suitable for acetylcholinesterase (AChE) activity examination. Michaelis constant and maximal velocity for 2,6-dichloroindophenol acetate were determined (38.0 µM and 244 pkat) and compared to the values for acetythiocholine (K(m) 0.18 mM; V(max) 5.1 nkat). Docking for 2,6-dichloroindophenol acetate and human AChE was done as well. In conclusion, 2,6-dichloroindophenol acetate seems to be suitable chromogenic substrate for AChE and spectrophotometry and based on this it can be easily performed whenever AChE activity should be tested.

Analysing deltamethrin susceptibility and pyrethroid esterase activity variations in sylvatic and domestic Triatoma infestans at the embryonic stage

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. Insects were collected from sylvatic areas, including Veinte de Octubre and Kirus-Mayu (Bolivia) and from domiciliary areas, including El Palmar (Bolivia) and La Pista (Argentina). Deltamethrin susceptibility was determined by dose-response bioassays. Serial dilutions of deltamethrin (0.0005-1 mg/mL) were topically applied to 12-day-old eggs. Samples from El Palmar had the highest lethal dose ratio (LDR) value (44.90) compared to the susceptible reference strain (NFS), whereas the Veinte de Octubre samples had the lowest value (0.50). Pyrethroid esterases were evaluated using 7-coumaryl permethrate (7-CP) on individually homogenised eggs from each population and from NFS. The El Palmar and La Pista samples contained 40.11 and 36.64 pmol/min/mg protein, respectively, and these values were statistically similar to NFS (34.92 pmol/min/mg protein) and different from Kirus-Mayu and Veinte de Octubre (27.49 and 22.69 pmol/min/mg protein, respectively). The toxicological data indicate that the domestic populations were resistant to deltamethrin, but no statistical contribution of 7-CP esterases was observed. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities. Moreover, this is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP).