石英对大鼠背根神经元高电压激活钙电流影响的探讨

Effects of Silica on the High-Voltage-Activated Calcium Current in Dorsal Root Ganglion of Rat

[目的]通过分析石英作用后大鼠背根神经元(DRG)高电压激活(HVA)钙电流的变化,探讨石英对钙离子通道结构和功能的影响。[方法]原代培养DRG,分0、5、15、45、135μg/mL5个石英浓度组进行体外染尘,运用全细胞膜片钳记录技术记录不同染尘时间DRGHVA钙电流,每组记录约6个DRG。[结果]135μg/mL剂量组石英作用于DRG后HVA钙电流密度峰值为(-95.9±38.8)pA/pF,大于对照组和低剂量组,差异有统计学意义(P<0.05),HVA钙电流从30%升至70%的速率明显快于对照组和其他染尘组,差异有统计学意义(P<0.01),但达峰时间差异无统计学意义(P>0.05);135μg/mL剂量组钙电流平均失活速率明显快于对照组和其他染尘组,差异有统计学意义(P=0.000),电流从峰值到记录结束时的下降率高于对照组和其他染尘组,差异有统计学意义(P<0.05)。45、135μg/mL组的DRG膜电导值分别为(1420.0±655.6)pS/μm2和(2257.4±454.2)pS/μm2,均高于对照组和低剂量染尘组,差异有统计学意义(P<0.05)。石英可使DRGHVA钙电流稳态激活曲线V1/2向正值方向移动约6.0～6.5mV,大于对照组,差异有统计学意义(P<0.05),移动的幅度与染尘浓度关系不明显(P>0.05);斜率k变化不明显(P>0.05)。石英作用后DRGHVA电流-电压(I-V)曲线形状改变不明显,对DRGHVA钙电流时间依赖性也没有明显影响。[结论]石英作用后DRGHVA钙通道结构和功能发生变化,使钙电流显著增大,呈激活快、失活也快的特征;另外,石英可使HVA钙通道在高刺激电压状况下(-10mV左右)更容易被激活。

[ Objective ] To explore the effect of silica on the structure and function of the calcium channel in dorsal root ganglion（ DRG ）of rat by analyzing the change of the high-voltage-activated（ HVA ）calcium current after silica exposure. [ Methods ] Primary DRG separated from rats was cultured, and exposed to various concentration of silica（ 0, 5, 15,45,135 μg/mL ）. Finally, the DRG HVA calcium current in whole-cell-patch-clamp-technique in different times was recorded （ about six DRGs in each group ）. [ Results ] The peak value of calcium current density in 135 μg/mL group was （ -95.9±38.8 ） pA/pF after DRG was exposed to silica and was obviously bigger than that in the control and other low dose groups （ P 〈 0.05 ）. The ascending slope （ from 30%-70% ）in 135 μg/mL group was significantly greater than that in the control and other exposure groups（ P 〈 0.01 ）; however, there was no obvious difference about the peak time between the test group and the control（ P 〉 0.05 ）. The mean decay speed of calcium current was also faster in the test groups than that in the control（ P = 0.000 ）, especially in 135 μg/mL group was notably faster than in the control and other test groups（ P = 0.000 ）. The decrease rate of current（ from the peak to recording end ）in 135 μg/mL group was obviously higher than that in the control and other test groups （ P 〈 0.05 ）. The membrane conductance of DRG in 45 μg/mL and 135 μg/mL group were（ 1 420.0 ± 655.6 ）and（ 2 257.4 ± 454.2 ）pS/μm^2 respectively, which were significantly higher than that in the control and other test groups（ P 〈 0.05 ）. V1/2 value of HVA calcium current steady-activation-curve in DRG shifted to right on abscissa about 6.0 to 6.5 mV and the differences were significant by comparison with the control, but there was no certain relation to dose and no obvious change about the value of k（ P 〉 0,05 ）. After silica exposure, there was no obvious influence on the current-voltage-curve and time-dependant of DRG HVA calcium current. [ Conclusion ] The structure and function of DRG HVA calcium channel is altered by silica and the inward calcium current increases evidently, with a characteristic of fast activation and also fast decay. In addition, after silica exposure, the HVA calcium channel seems easy to be activated under high test voltage （ around - 10mV ）.