OBJECTIVES: Organophosphate (OP) pesticides inhibit both red blood cell (RBC) and plasma cholinesterases (ChEs). Oximes, especially pralidoxime (2-PAM), are widely used as antidotes to treat OP poisoning. In addition, N-acetylcysteine (NAC) is sometimes used as an adjuvant antidote. The current study aimed to assess the feasibility of using NAC as a single therapeutic agent for OP poisoning in comparison to in vitro 2-PAM. METHODS: This study was carried out at the Razi Drug Research Center of Iran University of Medical Sciences, Tehran, Iran, between April and September 2014. A total of 22 healthy human subjects were recruited and 8 mL citrated blood samples were drawn from each subject. Dichlorvos-inhibited blood samples were separately exposed to low and high doses (final concentrations of 300 and 600 mumol.L-1, respectively) of 2-PAM, NAC and cysteine. Plasma and RBCs were then separated by centrifugation and their ChE activity was measured using spectrophotometry. RESULTS: Although cysteine-and not NAC-increased the ChE activity of both plasma and RBCs over those of dichlorvos, it did not increase them over those of a high dose of 2-PAM. CONCLUSION: These results suggest that the direct reactions of 2-PAM and cysteine with dichlorvos and the reactivation of phosphorylated ChEs occurr via an associative stepwise addition-elimination process. High therapeutic blood concentrations of cysteine are needed for the elevation of ChE activity in plasma and RBCs; however, both this agent and NAC may still be effective in the reactivation of plasma and RBC ChEs.
        
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Mohammadi H, Jalilian J, Karimi MY, Shetab-Boushehri SV (2017) In Vitro Cysteine Reactivates Organophosphate Insecticide Dichlorvos-Inhibited Human Cholinesterases Sultan Qaboos Univ Med J17: e293-e300
Mohammadi H, Jalilian J, Karimi MY, Shetab-Boushehri SV (2017) Sultan Qaboos Univ Med J17: e293-e300