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Hydrolysis of acetylthiocholine iodide and reactivation of phoxim-inhibited acetylcholinesterase by pralidoxime chloride, obidoxime chloride and trimedoxime

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The hydrolysis of acetylthiocholine iodide (ATCh) by pralidoxime chloride (2-PAM Cl), trimedoxime (TMB4) and obidoxime chlpride (LÜH6) was studied at pH 5.8–8.0 and incubation temperature from 5 to 40°C in vitro. Significant ATCh hydrolysis by 2-PAM Cl, TMB4 and LÜH6 was found, with the exceptions of those at pH 7.0, 6.2 and 5.8 at 5°C and those at pH 6.2 and 5.8 at 15°C. The hydrolysis by TMB4 and LÜH6 was significantly stronger than that by 2-PAM Cl. The hydrolysis increased with increasing pH, incubation temperature and three oxime or ATCh concentration. Significant hydrolysis of ATCh by the three oximes could be found when the terminal concentration of oxime was higher than 0.01 mM at pH 7.0 and 7.4 at 30 and 37°C. However, no hydrolysis of natural substrate (acetylcholine iodide) by the three oximes was found when very high terminal concentrations of oximes were used. In addition, the three oximes displayed an extraordinary efficiency in the reactivation of phoxim-inhibited acetylcholinesterase (AChE) from fish (Carassius auratus) or rabbit (Oryctolagus cuniculus domestic) brain in vitro. Parallel to the level of ATCh hydrolysis by the oximes, TMB4 and LÜH6 displayed significantly higher reactivation efficiency than 2-PAM Cl to phoxim-inhibited AChE. And, the extent of reactivation by 2-PAM Cl was also lower than the other two. Plausible antidotal actions of the oximes against organophosphate poisoning AChE and erroneously high estimation of AChE activity by the Ellman method were discussed.

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  • Alkodon M, Rao KS, Albuquerque EX (1988) Acetylcholinesterase reactors modify the functional properties of the nicotinic acetylcholine receptor ion chanal. J Pharm Exp Ther 245:543–556

    Google Scholar 

  • Calesnick B, Christensen JA, Richter M (1967) Human toxicity of various oximes. Arch Environ Health 15:599–608

    PubMed  CAS  Google Scholar 

  • Ellman GL, Courtney KD, Andress V, Featherstone MR (1961) A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem Pharmacol 7:88–95

    Article  PubMed  CAS  Google Scholar 

  • Eyer P (2003) The role of oximes in the management of organophosphorus pesticide poisoning. Toxicol Rev 22:165–190

    Article  PubMed  CAS  Google Scholar 

  • Hama H, Iwata T, Miyata T, Saito T (1980) Some properties of acethylcholinesterases partially purified from susceptible and resistant green rice leafhoppers, Nephotettix cincticeps UHLER (Hemiptera: Deltocephalidae). Appl Entomol Zool 15:249–261

    CAS  Google Scholar 

  • Hobbiger F (1976) Pharmacology of anticholinesterase agents. Neuromuscular junction. In: Zaimia E (ed) Handbush der Experimentellen Pharmakologie. Springer, Heidelberg, pp 487–581

  • Kassa J, Kuča K, Cabal J (2005) Comparison of the efficacy of current available oximes against tabun in rats. Biologia (Bratisl) 17:77–79

    Google Scholar 

  • Li JT, Zhang Y, Du XL, Sun MJ (2002a) Reactivation and aging of acxetylcholinesterase in human brain inhibited by phoxim and phoxim oxon in vitro. Chin J Prev Med 36:311–313

    Google Scholar 

  • Li JT, Zhang Y, Du XL, Sun MJ (2002b) Reactivation and aging of parathion- and paraoxon-inhibited human brain acetylcholinesterase in vitro. Chin J Pharmacol Toxicol 16:143–146

    CAS  Google Scholar 

  • Michel HO (1949) An electronic method for the determination of red blood cell and plasma cholinesterase activity. J Lab Clin Med 34:1564–1568

    CAS  Google Scholar 

  • Pannbacker RG, Oehme FW (2003) Pralidoxime hydrolysis to thiocholine esters. Vet Human Toxicol 45:39–40

    CAS  Google Scholar 

  • Reddy VK, Deshpande SS, Cintra WM, Scoble GT (1991) Albuquerque EX. Effectiveness of oximes 2-PAM and HI-6 in recovery of muscle function depressed by organophosphate agents in the rat hemidiaphragm. Fundam Appl Toxicol 17:746–760

    Article  PubMed  CAS  Google Scholar 

  • Sundwall A (1961) Minimum concentrations of N-methylpyridinium-2-aldoxime methane sulfonate (P2S) which reverse neuromuscular block. Biochem Pharmacol 8:413–417

    Article  PubMed  CAS  Google Scholar 

  • Tang QY, Feng MG (1997) Practical statistics and DPS data processing system. In: Tang QY, Feng MG (eds) DPS data processing system for practical statistics, China Agricultural Press, Beijing, pp 188–195

    Google Scholar 

  • Willema JL, De Bisschop HC, Verstraete AG, Declerck C, Christiaens Y, Vanscheeuwyck P, Buylaert WA, Vogelaers D, Colardyn F (1993) Cholinesterase reactivation in organophosphours poisoned patients depends on the plasma concentrations of the oxime pralidoxime methylsulphate and the organophosphate. Arch Toxicol 67:79–84

    Article  Google Scholar 

  • Worek F, Backer M, Thiermann H, Szinicz L, Mastu U, Klimmek R, Eyer P (1997) Resppraisal of indications and limitations of oxime therapy in organophosphate poisoning. Hum Exper Toxicol 16:466–472

    Article  CAS  Google Scholar 

  • Worek F, Kirchner T, Backer M (1996) Reactivation by various oximes of human erythrocyte acetylcholinesterase inhibited by different organophosphours compounds. Arch Toxicol 70:497–503

    Article  PubMed  CAS  Google Scholar 

  • Worek F, Widmann R, Knopff O (1998) Reactivating potency of obidoxime, prahdoxime, HI5 and HLO7 in human erythrocyte acetylcholinesterase inhibited by highly toxic organophosphorus compounds. Arch Toxicol 72:237–243

    Article  PubMed  CAS  Google Scholar 

  • Wu G, Miyata T (2005) Susceptibilities to methamidophos and enzymatic characteristics in 18 species of pest insects and their natural enemies in crucifer vegetable crops. Pestic Biochem Physiol 82:79–93

    Article  CAS  Google Scholar 

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This work was supported by Ministry of Science and Technology, China (Project No. 2005DFA30440) and Science and Technique Bureau of Fujian Province, China (Project No. 05I002).

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Correspondence to Gang Wu.

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Zhang, Y.H., Miyata, T., Wu, Z.J. et al. Hydrolysis of acetylthiocholine iodide and reactivation of phoxim-inhibited acetylcholinesterase by pralidoxime chloride, obidoxime chloride and trimedoxime. Arch Toxicol 81, 785–792 (2007).

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