Sakurada Koichi, Ikegaya Hiroshi, Ohta Hikoto, Akutsu Tomoko, Takatori Takehiko
National Research Institute of Police Science, 6-3-1, Kashiwanoha, Kashiwa, Chiba, Japan.
Toxicol Lett. 2006 Oct 25;166(3):255-60. doi: 10.1016/j.toxlet.2006.07.339. Epub 2006 Aug 12.
Pralidoxime iodide (2-PAM), an antidote approved for the reactivation of inhibited acetylcholinesterase (AChE) in organophosphate poisoning, dose-dependently hydrolyzed an acetylthiocholine iodide (ASCh). The AChE (0.3 U) activity inhibited by VX analog (ENMP, 0.1 microM) increased to approximately 200% of normal levels after a dosage of 5 mM 2-PAM (control 0.132+/-0.012 U/ml, 5 mM 0.253+/-0.026 U/ml). This result indicates that 2-PAM produced a thiocholine from the ASCh by hydrolysis. High-performance liquid chromatography (HPLC) analysis was then performed to further clarify the hydrolysis of ASCh with 2-PAM. It was clear that 2-PAM was converted to acetylated 2-PAM with acetic acid produced from ASCh by hydrolysis. Next, we tried to compare this esterase-like activity of 2-PAM with that of obidoxime, which is known as a strong reactivator of inhibited AChE, and with diacetylmonoxime, known as a weak reactivator. All of these oximes showed esterase-like activity, and their strengths were consistent with those of known reactivators of inhibited AChE. These results indicate that a great deal of the data obtained previously with ASCh relating to the effects of oximes must be rechecked. It is clear that oximes easily hydrolyze ASCh. We therefore strongly caution that the method of determining AChE activity with ASCh is not suitable for examining the effects of oximes.
碘解磷定（2-PAM）是一种被批准用于有机磷中毒时使受抑制的乙酰胆碱酯酶（AChE）重新活化的解毒剂，它能剂量依赖性地水解碘化硫代乙酰胆碱（ASCh）。被VX类似物（ENMP，0.1微摩尔）抑制的AChE（0.3单位）活性，在给予5毫摩尔2-PAM后增加到正常水平的约200%（对照组0.132±0.012单位/毫升，5毫摩尔组0.253±0.026单位/毫升）。这一结果表明2-PAM通过水解从ASCh产生了硫代胆碱。然后进行了高效液相色谱（HPLC）分析，以进一步阐明2-PAM对ASCh的水解作用。很明显，2-PAM被水解产生的乙酸转化为乙酰化的2-PAM。接下来，我们试图将2-PAM的这种酯酶样活性与作为受抑制AChE的强力重新活化剂的氯解磷定以及作为弱重新活化剂的双乙酰单肟的酯酶样活性进行比较。所有这些肟都表现出酯酶样活性，其强度与已知的受抑制AChE重新活化剂的强度一致。这些结果表明，以前用ASCh获得的许多与肟的作用相关的数据必须重新检查。很明显，肟很容易水解ASCh。因此，我们强烈警告，用ASCh测定AChE活性的方法不适用于研究肟的作用。
