有机磷杀虫剂所致的神经肌接头病的生化机制研究

Potential biochemical mechanisms of neuromuscular junction transmission dysfunction induced by organophosphorus insecticides

目的 探讨有机磷杀虫剂 (OPs)引起的神经肌接头传导功能异常的生化机制。方法 用肟硫磷 (114 4mg/kg)染毒大鼠制作肌无力模型 ,用电刺激频率为 2 0Hz的单纤维肌电图 (SSFEMG)检测染毒大鼠平均连续差 (MCD)评价其神经肌接头传导功能 ,检测腓肠肌Ca2 + ATP酶、Na+ ,K+ ATP酶、cAMP依赖性蛋白激酶 (PKA)、Ca2 + /磷脂依赖性蛋白激酶 (PKC)和酪氨酸蛋白激酶 (TPK)活力 ,并用免疫组织化学法检测比目鱼肌中丝氨酸 (Ser)、苏氨酸 (Thr)和酪氨酸 (Tyr)残基的磷酸化程度。结果 与对照组和肌力正常的染毒大鼠相比 ,肌无力大鼠各指标的变化如下 :(1)MCD明显增高 ;(2 )腓肠肌Ca2 + ATP酶、Na+ ,K+ ATP酶和PKA活力明显下降 ,且与MCD呈显著负相关 (r =- 0 .5 82、- 0 .713、- 0 .5 0 6 ,P <0 .0 5 ) ;(3)腓肠肌PKC和TPK活力明显增高 ,且与MCD呈显著正相关 (r=0 .72 3、0 .5 89,P <0 .0 5 ) ;(4)Ser磷酸化程度明显减弱 ,Tyr磷酸化程度明显增强。结论 OPs引起的神经肌接头传导功能异常可能与Ca2 + ATP酶和Na+ ,K+ ATP酶活力下降引起的肌肉兴奋性减低 ,以及Tyr磷酸化增强和Ser磷酸化减弱引起的烟碱样乙酰胆碱受体失敏加速、复敏延迟有关。

Objective To explore the potential biochemical mechanisms of neuromuscular junction transmission(NMJT) dysfunction induced by organophosphorus insecticides. Methods Ten rats were dosed with phoxim(1 144 mg/kg) and 5 of them developed myasthenia.The NMJT function was evaluated by the mean consecutive differences(MCD) measured by stimulation single fiber electromyography(SSFEMG) with the frequency of stimuli at 20 Hz.The activity of Ca 2+ -ATPase,Na +,K +-ATPase,cAMP dependent protein kinase(PKA),Ca 2+ /phospholipid dependent protein kinase(PKC),and tyrosine protein kinase(TPK) were determined. Results In comparison with the control and non-myasthenic rats,the results in myasthenic rats showed that:(1)?the MCDs increased;(2)?the activities of Ca 2+ -ATPase,Na +,K +-ATPase and PKA decreased and were negatively correlated with MCD;(3)?the activities of PKC and TPK increased,and were positively correlated with MCD;(4)?the phosphorylation of serine residuals in sarcolemma was weaker and the phosphorylation of tyrosine residuals was stronger. Conclusions The NMJT dysfunction is likely associated with the decrease in Ca 2+ -ATPase and Na +,K +-ATPase activity.The acceleration of desensitization and prolongation of resensitization of nicotinic acetylcholine receptors occur following the increase in tyrosine phosphorylation and the decrease in serine phosphorylation induced by OPs poisoning.