L型电压门控钙通道α1D亚型在小鼠听力平衡及心脏起搏传导中的意义

Mice lacking of voltage-gated L-type calcium channel α1D subunit have impaired sinoatrial node function and caused deafness

目的:培育L型电压门控钙通道(LTCCs)α1D亚型的基因突变纯合子(α1D-/-)小鼠、杂合子(α1D+/-)小鼠及野生型(α1D+/+)小鼠模型,并利用这3种不同基因型小鼠研究α1D通道亚基在内耳听觉平衡功能及心脏起博传导中的作用。方法:利用同窝生不同基因型小鼠为实验对象,采用听觉脑干反应(ABR)和耳蜗内电位(EP)检测技术和心电图(ECG)检测技术,检测和观察各基因型小鼠听觉功能、EP及ECG的PP间期和PR间期。利用游泳实验和滚桶实验检测各个基因型小鼠的平衡功能。结果:α1D+/+小鼠的听力正常,ABR的短声(Click)阈值为(34.8±5.7)dBSPL;EP均值为(105.3±3.1)mV。α1D+/-小鼠听力低于同窝α1D+/+小鼠,ABR的短声阈值为(54.4±12.4)dBSPL,α1D+/-小鼠的EP为(75.8±9.9)mV,其平衡功能正常。α1D-/-小鼠呈现全聋,ABR在100dB无反应100dBSPL,其EP值为(48.6±19.3)mV;α1D-/-小鼠表现出听觉功能丧失但其平衡功能正常。心电图检测显示α1D+/+小鼠心律正常;α1D+/-小鼠和α1D-/-小鼠显示出心动过缓、RR间期延长;α1D-/-小鼠的心率最慢。α1D+/-小鼠出现窦性心动过缓(RR间期:146±1.4ms),与α1D+/+小鼠的相比较[(117±0.4)ms]其RR间期明显延长,差异有统计学意义(P<0.05)。α1D-/-小鼠和α1D+/-小鼠有窦性心动过缓和房室传导阻滞,RR间期和PR间期均延长。α1D-/-小鼠的PR间期延长[(53±0.5)ms],与α1D+/+小鼠的(PR间期:38±0.3ms)相比,差异有统计学意义(P<0.05);α1D-/-小鼠的RR间期[(244±2.9)ms]延长,与α1D+/-小鼠[(146±1.4)ms]相比,差异有统计学意义(P<0.05)。结论:LTCCsα1D亚型是维持内耳听觉生理的关键钙通道,α1D通道亚型的缺失或功能受限均可导致影响听觉生理功能。但α1D亚基的缺失不影响小鼠的平衡功能,表明α1D亚基在前庭系统中的功能作用有限。LTCCsα1D亚型在心脏起博传导系统中也具重要生理作用。

Objective： L-type voltage-gated calcium channel subunit α1D-/- mice（homozygous mutant, knockout） ,α1D＋/-（heterozygous） and α1D＋/＋（wild-type） have played role in L-type voltage-gated calcium channel α1D subunit in auditory function of inner ear as well as sinoatrial node function of the mice. Method： Hearing threshold and endocochlear potential （EP） were measured in the aid knockout mice, heterozygous mice and wild-type mice by auditory brainstem response（ABR）, EP recordings and Electrocardiograph（ECG） respectively. To assessment of the vestibular function of the mice, the ability of Balancing was performed by a swim test and a horizontal cylinder test. Result： The auditory function of α1D＋/＋ mice were normal, the mean value for ABR thresholds in response to click sound stimulus was （34.8±5.7）dB SPL,EP was （105.3±3.1）mV. The mean value for ABR thresholds in response to click sound stimulus was elevated in α1D＋/- mice was （54.4±12.4）dB SPL, relative to that observed in α1D＋/＋ mice significantly increased（ P 〈0.05） ; EP of α1D＋/- mice was about （75.8＋9.9）mV. α1D-/- mice were completely deaf, the ABR wave form was not observed for even 100 dB SPL sound stimuli used and EP was still remain in （48. 6＋ 19. 3）mV. α1D knockout mice were deaf and demonctrated no vestibular defect, α1D＋/- and α1D-/- mice show significant sinus bradycardia with significant prolongation of the RR interval（146± 1.4 and 244±2.9, respectively） comparing to the α1D＋/＋ wild-type mice （117±0.4） in the same littermates. In addition, the homozygous α1D-/- show a significant prolongation of the PR interval （53±0.5）compared to that of the α1D ＋/＋ wild-type mice（38±0.3）. Conclusion： L-type vohage-ga ted calcium channel α1D subunit plays a critical role in calcium homeostasis in the inner ear. Mice lacking of α1D calcium channel gene would lead to influence auditory function and sinoatrial node dysfunction subsequently.