氯化镧对大鼠海马即刻早期基因表达的影响

Effects of lanthanum chloride on the expression of immediate early genes in the hippocampus of rats

目的 研究氯化镧（1anthanumchloride，LaCl3）对大鼠海马即刻早期原癌基因（c-jun）、早期生长反应基因1（early growth response gene1，Egrl）和活性调节细胞骨架基因（activity—regulatedcytoskeletalgene，Arc）表达的影响，探讨LaCl3损害学习记忆能力的机制。方法按完全随机化法将40只Wistar雌性成年大鼠分为对照组和低（0．25％）、中（0．50％）、高（1．00％）LaCl3染毒组，各组雌鼠10只，与5只雄鼠按2：1比例交配。对照组和低、中、高剂量染毒组产仔鼠数分别是80、83、78、75只。各LaCl3染毒组仔鼠断乳前吸吮母乳染镧，断乳后饮用0．25％、0．50％和1．0HD％LaCl3溶液1个月。分别采用跳台试验测试仔鼠学习记忆能力，电感耦合等离子体质谱仪测定海马镧含量，RT—PCR法检测海马c-jun、Egr1和ArcmRNA表达，采用Westernblotting法检测海马c-jun、Egr1和Arc蛋白表达。结果低、中、高剂量组仔鼠在跳台测试时错误次数分别是（1．75±0．71）、（2．38±0．92）、（3．00±0．76）次，中、高剂量组均高于对照组的（1．25±0．46）次（q值分别为4．386、6．793，P值均〈0．05）；潜伏期分别为（174．13±33．72）、（139．25±45．83）、（75．50±18．56）S，均低于对照组的（206．754-20．47）S（q值分别为2．958、6．121、11．902，P值均〈0．05）。对照组和低、中、高剂量组仔鼠海马c-junmRNA表达量分别为（0．89±0．08）、（0．77±0．12）、（0．58±0．14）、（0．29±0．11），c-jun蛋白表达量分别为（0．72±0．13）、（0．64±0．11）、（0．43±0．11）、（0．31±0．14），Egr1mRNA表达量分别为（0．78±0．09）、（0．61±0．13）、（0．53±0．10）、（0．22±0．08），Egr1蛋白表达量分别为（0．65±0．18）、（0．40±0．15）、（0．32±0．13）、（0．14±0．09），均与染毒剂量具有剂量一反应关系，相关系数r值分别为-0．900（t=11．309，P=0．000）、-0．969（t=7．058，P=0．000）、-0．898（t=11．179，P=0．000）和-0．962（t=6．739，P=0．000）。结论LaCl3损害大鼠学习记忆能力的机制可能与其致海马c-jun和egr1基因和蛋白表达降低有关。

Objective To study influence of lanthanum chloride （ LaCl3 ） on the expression of immediate early genes （lEGs） including e-jun, early growth response gene 1 （Egr1） and activity-regulated eytoskeletal gene （ Arc ） in the hippocampus of rats, and discuss the mechanism of LaCl3 undermining learning and memory capability. Methods Forty female Wistar adult rats were divided into control group, low LaCl3-contaminated group （ 0. 25% ） , medium LaCl3-contaminated group （ 0. 50% ）, and high LaCl3-contaminated group （ 1.00% ） by randomized design. Each group had ten female rats along with five male rats and mated by the ratio of 2： 1. The amounts of pups in the above four groups were 80,83,78 and 75 separately. The pups in respective group were La-dyed by lactation, and then the pups in LaCl3-contaminated groups drank 0. 25% ,0. 50% and 1.00% LaCl3 separately for one month. Learning and memory capability of pups were measured in jumping stairs experiment. Hippocampal lanthanum content was determined by inductively coupled plasma mass spectrometry （ICP-MS）. Hippocampal c-jun, Egrl and Arc mRNA expression was detected by RT-PCR, and corresponding protein expression was measured by Western blotting method. Results In the jumping stairs experiment, pups in 0.25% , 0. 50% and 1.00% LaCl3-contaminated groups respectively made （ 1.75±0. 71 ）, （2. 38±0. 92） and （3.00±0. 76） mistakes; significantly higher than control group （ 1.25 ±0. 46） （q values were d. 386,6. 793 ,P 〈0. 05 ）. However, the incubation period of 0. 25% ,0. 50% and 1.00% LaCl3-contamihated groups were （ 174. 13 ± 33.72） , （ 139.25± 45.83 ） and （75.50 ± 18.56） respectively, which were all significantly lower than that of control group （206. 75 ± 20. 47 ） （ q values were 2. 958,6. 121,11. 902, P 〈 0. 05 ）. Hippocampal c-jun mRNA expression were （0.89±0.08）,（0.77 ±0.12）,（0.58 ±0.14） and （0.29±0.10）; while the c-jun protein expression were （ 0. 72 ± 0. 13 ）, （ 0. 64± 0. 11 ）, （ 0. 43 ± 0. 11 ） and （ 0. 31 ± 0. 14 ）, and the Egrl mRNA expression were （0. 78±0. 09）, （0. 61 ±0. 13）, （0. 53 ±0. 10） and （0. 22 ±0. 08） ,Egrl protein expression were （0.65±0.18）,（0.40±0.15）,（0.32±0.13） and （0.14±0.09） in0.25%,0.50% and 1.00% LaCl3-contaminated groups; and all of which presented a dose-effect relationship that the correlation coefficients of these parameters with dose were - 0. 900 （ t = 11. 309, P = 0. 000） , - 0. 969 （ t = 7. 058,P = 0. 000）, - 0. 898 （ t = 11. 179, P = 0. 000 ） and - 0. 962 （ t = 6. 739, P = 0. 000 ）. Conclusion LaC13 undermines the learning and memory capability of rats ,which is possibly related to lower expression of c-jun and Egrl gene and protein induced by lanthanam in hippocampus.