Effect of four organophosphorus compounds on human blood acetylcholinesterase: in vitro studies.

In the present investigation acetylcholinesterase (AChE) was estimated in erythrocytes from blood samples exposed to four commonly used organophosphorus pesticides in vitro. The aim of the study was to determine the IC50 concentration of the pesticides monocrotophos, chlorpyrifos, profenofos, and acephate as inhibitors of AChE. Cholinesterase was spectrophotometrically measured using acetylthiocholine iodide (AChI) as substrate and dithiobisnitrobenzoic acid (DTNB) as the coloring agent using different aliquots of the pesticides. It was found that as the concentration of the pesticides increased, the inhibition also increased, and a dose-response relationship was obtained in a time-dependent manner. The IC50 values for RBC-AChE were 0.12 muM, 0.25 muM, 0.35 muM, and 4.0 muM for chlorpyrifos, monocrotophos, profenofos, and acephate, respectively. Chlorpyrifos was found to be a more potent inhibitor of AChE followed by the rest of the pesticides used in this study. This investigation determined the relative toxicities of organophosphorus pesticides under laboratory conditions using statistical methods.