A comparison of two methods for the measurement of cholinesterase inhibition in human blood

Anticholinesterase effects of carbamate insecticide thiofanox and its metabolites in rats

“…There are discrepancies in in vivo ChE inhibition values among different laboratories for measuring blood ChE in carbamate poisoning. These discrepancies are due to sample dilution, substrate concentration, long reaction time, and washing of packed RBC (Witter, 1963; Winteringham and Fowler, 1966;Disney, 1966;Chin and Sullivan, 1968). All these factors influence the dissociation rate of the carbamate-enzyme complex and therefore result in underestimation of the degree of carbamate inhibition.…”

Carbamate poisoning. Effect of certain carbamate pesticides on esterase levels in the pheasant (Phasianius colchicus) and pigeon (Columba livia)

“…Since the carbamylated intermediate often breaks down spontaneously, many methods of measurement can underestimate the degree of inhibition which occurs in vivo especially if the formation or maintenance of equilibrium levels of the complex is discouraged by dilution of the tissue extracts whose activity is to be measured, by the use of high substrate concentrations or by carrying out the assay slowly. The dependence of the results on these factors has been amply demonstrated (Winteringham and Disney, 1964;Disney, 1966;Winteringham and Fowler, 1966). We chose to retain our original ChE assay (Bunyan et al, 1968a) since we seek to maintain a standard approach to field investigations, and although it employs a high substrate concentration and a diluted tissue extract it has the advantage of being a dynamic method which can be applied rapidly to the extract.…”

“…treatments. During measurement of esterase levels where carbamate inhibition has occurred it has been extensively reported (Winteringham and Disney, 1964;Disney, 1966;Winteringham and Fowler, 1966) that high substrate concentrations and dilution of the esterase preparation can lead to a reversal of carbamate inhibition. However, in order to allow comparison to be made with the results obtained from previous organophosphorus feeding experiments no changes were made in the assays previously described (Bunyan et al, 1968a).…”