THE EFFECTS OF OXIMES IN THE ASSAY OF ACETYLCHOLINESTERASE ACTIVITY IN LYSED ERYTHROCYTES IN VITRO

Abstract

Organophosphorus compounds are known to inhibit the esteratic site of acetylcholinesterase by phosphorylation. The phosphorylated esteratic site of acetylcholinesterase undergoes hydrolytic regeneration at a slow or negligible rate. Nucleophilic agents such as hydroxytamine, hydroxamic acids, and oximes reactivate the enzyme more erapidfy than does spontaneous hydrolysis. The red cell cholinesterose activity was assayed using dithio bis-2-nitrobenzoic acid (DTNB) commonly known as Ellman's reagent. The principle of this assay method is the rate of hydrolysis of acetylthiocholine (substrate) by a red celt suspension. Thiocholine that is produced, forms a yellow complex, when EUman's reagent (DTNB) is used in the assay. This was tested in vitro in lysed erythrocyte samples of 35 healthy persons who had no known exposure to cholinesterose inhibitors, after the observation of immediate increase in absorption of light at 440 nm. All of data were statistically analyzed using one-way ANOVA and student t-test. A value of p<0.01 was considered. Results of this study show an increased absorbance in 440 nm, for pretreated samples with pratidoxime. This was observed by doses of (0.1, 0.5, 1,2 mmol, p<0.01). It was also a good dose dependent increase in absorbance at 440 nm for pralidoxime, (r=0.940, p<0.01). Also there is a significant increase in absorbance at 440 nm for samples pretreated by obidoxime at doses of (0.1, 0.5, 1,2 mmol). There is also a good correlation between absorbance at 440 nm and variou doses of obidoxime (r=0.946 , p<0.01). It is concluded that oximes can hydrofyzes the substrate, which then would be a source of error in determination of acetylcholinesterase activity and must be token into account.