Apoptosis of neuron DRG on dorsal root of rat induced by rare-earth ions including La³⁺, Gd³⁺, Yb³⁺, etc. as well as its influence on K⁺-channel of membrane were studied. DRG cell of rat was acutely separated and treated with different concentration of LaCl₃, GdCl₃ and YbCl₃ for 96h, then, inspected the apoptosis of cell by flow cytometer. Whole-cell patch clamp method was used to record the influence of La³⁺, Gd³⁺ and Yb³⁺ on the current of different K⁺-channel of cell membrane. The results showed that: apoptosis rate of cell increased without significant difference after the neuron DRG was treated with LaCl₃ and GdCl₃ of 10, 100 and 1000 μmol/L for 96h;  the apoptosis rate of cell treated with three concentration groups of YbCl₃ for 96h increased and had significant difference compared with control group. La³⁺, Gd³⁺ and Yb³⁺ of 100μmol/L outside the cell inhibited the transient outward potassium current I_A, and the activation as well as inactivation of I_A significantly shifted to the right, La³⁺ had weakest effect while Yb³⁺ had strongest effect; La³⁺, Gd³⁺ and Yb³⁺ inside the cell inhibited and delayed the rectifier potassium current I_K while the effect of inhibition also displayed upward tendency, La³⁺ and Gd³⁺ of 100μmol/L rarely influenced the activation of I_K while the activation of I_K shifted to the right by Yb³⁺. La³⁺, Gd³⁺ and Yb³⁺ outside the cell increasingly inhibited I_A and delayed the activation of I_A which might increase the excitatory of neuron as well as maintained the neuron continue the state of urge; La³⁺ and Gd³⁺ inside the cell would not influence the activation of I_K, and it might release the sustained depolarization of neuron induced by La³⁺ and Gd³⁺ outside the cell, it might be one reason to interpret why DRG did not appear significant difference within the concentration scope of our study; however, Yb³⁺ delayed the activation of I_K and inhibited the growth of K⁺ current more significantly which might enhance the excitatory of neuron induced by the Yb³⁺ outside the cell as well as lead to the apoptosis of neuron DRG, this might be the reason to interpret why the cell hatched by Yb³⁺ never appeared apoptosis within 24h but appeared apoptosis with 96h, because sustained depolarization of neuron enhanced La³⁺ outside the cell entering from cell membrane into cell to influence I_K , and induced apoptosis as the hatching time passing through. Conclusions: as exogenous and endogenous signals, rare-earth ions including La³⁺, Gd³⁺, Yb³⁺, etc. influenced neuron DRG and had different influence on different position inside/outside the cell as well as the protein was adjusted by different ways; one reason for inducing the apoptosis of neuron was that rare-earth ion implemented apoptosis effect by influencing the I_K channel after entering into cell; Yb³⁺ had relative heavier neurotoxicity than La³⁺ and Gd³⁺.

 

The document about channel of membrane was translated by Huayiwang Mandarin Translation Company.

 

研究了La³⁺,Gd³⁺,Yb³⁺三种稀土离子诱导大鼠背根神经元DRG凋亡以及对膜上钾离子通道的影响。急性分离大鼠DRG细胞，用不同浓度的LaCl₃、GdCl₃、YbCl₃处理DRG细胞96h,采用流式细胞仪检测细胞的凋亡情况。利用全细胞膜片钳法，记录LaCl₃、GdCl₃、YbCl₃对细胞膜上不同钾通道电流的影响。结果表明： 10、100、1000 μmol/L LaCl₃和GdCl₃处理DRG神经元96 h，细胞凋亡率递增，但都不具有显著差异；三个浓度组YbCl₃处理96h，细胞的凋亡率递增，与对照组相比都具有显著差异。胞外100μmol/L的La³⁺,Gd³⁺,Yb³⁺抑制瞬间外向钾电流I_A，使I_A的激活和失活过程都显著右移，抑制和右移的程度是La³⁺最弱，Gd³⁺次之，Yb³⁺最强；胞内的La³⁺,Gd³⁺,Yb³⁺抑制延迟整流钾电流I_K，抑制的程度也呈增长趋势，100μmol/L La³⁺和Gd³⁺基本不影响I_K的激活，Yb³⁺使I_K的激活右移。胞外的La³⁺,Gd³⁺,Yb³⁺呈增长的趋势抑制I_A，推迟I_A的激活，这会增加神经元的兴奋性，使神经元持续发动冲动状态；胞内的La³⁺和Gd³⁺不影响I_K的激活，这种行为可能会缓解胞外的La³⁺和Gd³⁺引起的神经元持续去极化，可能是DRG在我们研究的浓度范围内不出现显著凋亡的原因，而Yb³⁺使I_K的激活推迟且其抑制钾电流的程度也大，这可能会进一步加强胞外Yb³⁺引起的神经元兴奋，导致DRG凋亡,这可能也是为什么Yb³⁺孵育细胞24 h不出现凋亡，而96 h却出现凋亡的原因吧，因为随着孵育时间的延长，持续去极化使胞外的Yb³⁺通过细胞膜进入细胞内部通过影响I_K而诱导凋亡。结论：稀土离子La³⁺,Gd³⁺,Yb³⁺作为外源性信号和内源性信号对DRG神经元施加影响，在胞内外的结合位点不同，调控的蛋白途径不同；诱导神经元凋亡的原因之一是稀土离子进入胞内影响I_K通道实施凋亡效应；Yb³⁺较La³⁺和Gd³⁺的神经毒性强。

 

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