Study On Hydrolysis Of Acetylthiocholine-iodide And Reactivation Of Acetylcholinesterase By Oximes

The objectives were investigated in this thesis, i.e., (1) the hydrolysis of acetylcholine iodide and acetylthiocholine iodide (ATCh) by pralidoxime chloride (2-PAM-Cl), trimedoxime (TMB) and obidoxime Chloride (L(?)H₆) at different pH, incubated temperature, reaction time and concentration of oximes or acetylcholine; (2) the ability to reactivations of phoxim-poisoned AChE by the three oximes; (3) the reactivation and aging of phoxim-poisoned acetylcholinesterase (AChE) by the three oximes. The results revealed:1．Non-classical functions of the three oximes: comparison on the hydrolysis of ATCh.(1) It was indicated that the ATCh was hydrolyzed by three oximes significantly. The hydrolysis increased corresponding to the increase of pH and incubation temperature or time. For instance, by TMB₄ at 30 deg.C, the OD₄₁₂ values increased from 0．90 to 2．08 corresponding to the increase of incubation pH from 7．0 to 8．0．If the incubation temperature increased from 5 to 30 deg.C, the OD₄₁₂ increased from 0．028 to 0．94 after the reaction system was incubated for 2 h.(2) When pH is below 6．2, ATCh was hydrolyzed minutely by three oximes. For example, when incubated 37 deg.C, after incubated for 4h, the OD₄₁₂ is only 0．29．however, When the pH increased to 7．0 , it was hydrolyzed significantly.(3) ATCh was hydrolyzed stronger and stronger by three oximes with the concentrations of oximes increasing. For example, when pH is 7．0, the ATCh concentration is 0．6 mmol/L and the 2-PAM-Cl concentration is 0．001, 0．01, 0．05, 0．1, 0．2 and 0．5 mmol/L, respectively, after incubated 30 deg .C for 20 min the OD₄₁₂ is 0．0013, 0．0057, 0．0387, 0．1037, 0．2313 and 0．6083, respectively.(4) ATCh was hydrolyzed stronger and stronger by three oximes with the concentrations of ATCh increasing. For example, when pH is 7．0, the 2-PAM-Cl concentration is 0．05 mmol/L, the ATCh concentration is 0．006, 0．06, 0．12 and 0．6 mmol/L, respectively, after incubated 30 deg.C for 20 min the OD₄₁₂ is 0．00, 0．0023, 0．0100 and 0．0670, respectively.(5) ATCh was hydrolyzed stronger by TMB₄ and L(?)H₆ than 2-PAM-Cl in the same condition. For example, when pH is 7．0, the oxime is 2-PAM-Cl, TMB₄ and L(?)H₆, after incubated 30 deg.C for 4 h the OD₄₁₂ is 0．2715, 1．4487 and 1．436, respectively.(6) Hydrolysis of acetylcholine-iodide and ATCh by three oximes were measured by the pH method of Michel. It was showed that ATCh was hydrolyzed by three oximes, but acetylcholine-iodide was not. It was also revealed that ATCh was hydrolyzed stronger by 2-PAM-Cl than by the other two in the same condition. For example, when pH is 8．0, the oxime is 2-PAM-Cl, TMB₄ and L(?)H₆, after incubated 25 deg.C for 1 h the cuvette which added ATCh had the pH decrease of 0．8625, 0．582 and 0．678, respectively. However, the cuvette which added acetylcholine iodide had the pH decrease of 0．0158, 0．0584 and 0．0299, respectively.2．The toxicity of AChE by phoximThe results showed: The I₅₀ 's inhibition of the AChE from Plutella xylostella, Cotesia plutellae, Musca domestica, Blattella germanica, carassius auratus brain, oryctolagus cuniculus domestic brain and cairina moschata was 1．8×10^-4 , 4．0×10^-5 , 6×10^-6 , 4．2×10^-5 , 1．8×10^-4 , 2．4×10^-4 and 9×10^-4 , respectively.3．The K_aging, the half aging time and the 99% aging time of phoxim-AChEThe K_aging of phoxim-poisoned diamondback moth, Cotesia plutellae, Blattella germanica, carassius auratus and oryctolagus cuniculus domestic AChE was 0．0129, 0．0143, 0．0111, 0．0105, 0．0173, respectively. The half aging time (t_0．5 ) of AChE was 53．7 h, 48．5 h, 62．4 h, 66 h and 40．06 h respectively. And the 99% aging time is 357．0 h, 322．0 h, 414．9 h, 438．6 h and 266．2 h, respectively.In our study the poisoned cairina moschata AChE by phoxim had not been reactivated by there oximes. And poisoned sensitive Musca domestica AChE did not aged.5．The ability to reactivate the phoxim-poisoned AChE by the three oximesThe reactivations by TMB and L(?)H₆ were obviously different from 2-PAM-Cl. On the equivalent molar basis, the potency of TMB and L(?)H₆ was higher in reactivation of inhibited carassius auratus brain and oryctolagus cuniculus domestic brain than that of 2-PAM-Cl. However, there is no coherence between The reactivations of Blattella germanica AChE, Musca domestica AChE, Cotesia plutellae AChE and Plutella xylostella AChE.