内皮依赖性舒张因子对豚鼠内耳微循环障碍所致听力损伤的保护作用

The protective action of endothelium derived relaxing factor on cochlear function during experimental cochlear ischemia in guinea pigs

目的 :探讨内皮依赖性舒张因子 (EDRF/NO)对听功能的保护作用及作用机制。方法 :36只豚鼠随机分为 4组 ,利用活体显微镜、电视摄像、计算机图像分析技术及螺旋韧带血管纹铺片、透射电镜技术 ,观察EDRF/NO对听功能的保护作用。同时 ,以听神经复合动作电位阈值 ,判断听力损伤程度 ,测定循环血液中超氧化物歧化酶(SOD)的浓度 ,以反映微循环血液中氧自由基的含量。结果 :①生理盐水组 ,耳蜗微循环的血流量在整个测试的 30min内保持稳定 ,听功能正常 ;②速尿组 (F组 ) ,经静脉注射药物后 ,耳蜗血流迅速下降 ,在用药 10min时 ,耳蜗血流下降达 5 6 % ,缺血的同时伴听力下降、耳蜗血管纹超微结构的损伤及循环SOD的下降 ,与用药前比较差异有显著性 ;③速尿 /L 精氨酸组 (F/L Arg组 ) ,EDRF/NO能使速尿引起的血流下降明显改善 ,听功能及耳蜗血管纹超微结构的损伤程度较单纯F组减轻 ,恢复正常功能的时间提前 ;④速尿 /L 硝基 精氨酸组 (F/L NNA组 ) ,耳蜗的缺血及听力损伤的程度均较F组加重 ,且恢复正常的时间延长。结论 :EDRF/NO能通过加快豚鼠内耳微循环的血流 ,增加局部血流的灌注 。

Aim: To investigate the protective action of endothelium derived relaxing factor(EDRF/NO) on cochlear microcirculation.Methods: The total of 36 guinea pigs were randomly divided into 4 groups. Cochlear function was assessed using compound action potential audiogram before and after intravenous administration,and the content of free oxygen radicals was assessed by testing superoxide dismutase,a free oxygen radicals eraser. Results:①In control group,there was no change in cochlear blood flow (CoBF) and cochlear function was normal during the entire test process.②In frusemide group(F Group), CoBF decreased acutely after intravenous;infusion of frusemide and CoBF was below baseline 56% in 10 minutes.Meantime,hearing function was impaired and SOD decreased in plama level.Simultaneously the ultrastructure of stria vascularis was damaged.Comparing with the CoBF and SOD prior to the treatment,there were significant differences.③In F/L Arg group,CoBF reduced and the impairment of the ultrastructure of stria by frusemide could be significantly ameliorated and recovered rapidly with intravenous L Arg. The impairment of hearing function was milder than that of F group.④In F and F/L NNA group,the impairment of hearing function and CoBF decreased more severely than those of F group,and the threshold in this group recovered more slowly than that in F group.Conclusion: These findings demonstrate that EDRF/NO may improve the flow of microcirculation in inner ear by increasing the red blood cell velocity,and erase free oxygen radicals.The evidences provided in this study may contribute to further using of EDRF/NO in treatment of hearing loss due to microcirculation disorder in inner ear.