THE ORIGINS AND MECHANISM OF GLUTAMATE RELEASE IN COCHLEA

耳蜗谷氨酸释放的起源和机制

• 批准号: 11671692
• 负责人: MATSUDA Keiji
• 金额: $ 2.3万
• 依托单位: Miyazaki Medical College
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11671692/
• 关键词: glutamate; microdialysis; fluorometric assay; perilymph; drug-induced ototoxicity; ischemia; extracellular calcium; calcium dependency; 薬剤性内耳障害; カナマイシン; エタクリン酸

We applied microdialysis technique to investigate the perilymphatic glutamate. The glutamate concentration was analyzed continuously by enzyme-linked fluorometric assay combined with microdialysis. (1) The time course of changes in perilymphatic glutamate were observed during the application of kanamycin and ethacrynic acid, which are known to damage the hair cells in the inner ear. In guinea pigs receiving a loading dose of 800 mg/kg of kanamycin subcutaneously, followed three hours later by an intravenous injection of 40 mg/kg of ethacrynic acid, a marked glutamate release was clearly found about 2 hours after the injection of ethacrynic acid. The present findings provide additional evidence that glutamate acts as an aggravating factor in aminoglycoside-induced ototoxicity. (2) A glutamate release observed in the same model shown above was completely inhibited in the absence of extracellular Ca^<2+>. This observation shows extracellular Ca^<2+> play an important role in drug-induced ototoxicity. (3) The time course of changes in perilymphatic glutamate were studied in the normal or deaf guinea pig cochlea during cardiac arrest. In normal animal slightly efflux of glutamate was observed within 10 min after cardiac arrest. This was completely inhibited in the absence of extracellular Ca^<2+>. Marked glutamate efflux only occurred 10 min after cardiac arrest in Ca^<2+>-independent manner. In deaf animals there was no glutamate release in 1 hr after cardiac arrest. The present findings suggest that during the cardiac arrest, most of the released glutamate is of non-vesicular origin, probably from both inner and outer hair cells.

我们应用微透析技术来研究外淋巴谷氨酸。通过酶联荧光测定结合微透析连续分析谷氨酸浓度。 (1)在应用卡那霉素和依他尼酸期间观察外淋巴谷氨酸变化的时间过程，已知卡那霉素和依他尼酸会损伤内耳毛细胞。豚鼠皮下注射800mg/kg卡那霉素负荷剂量，三小时后静脉注射40mg/kg依他尼酸，在注射依他尼酸约2小时后，明显发现谷氨酸释放明显。目前的研究结果提供了额外的证据，表明谷氨酸是氨基糖苷类引起的耳毒性的加重因素。 (2)在不存在细胞外Ca 2+ 的情况下，在上述相同模型中观察到的谷氨酸释放被完全抑制。该观察结果表明细胞外Ca 2+ 在药物诱导的耳毒性中发挥重要作用。 (3)研究了心脏骤停期间正常或聋豚鼠耳蜗外淋巴谷氨酸变化的时间过程。在正常动物中，心脏骤停后 10 分钟内观察到谷氨酸轻微流出。这在不存在细胞外Ca 2+ 的情况下被完全抑制。明显的谷氨酸流出仅在心脏骤停后10分钟以不依赖Ca 2+ 的方式发生。聋哑动物心脏骤停后 1 小时内没有谷氨酸释放。目前的研究结果表明，在心脏骤停期间，大部分释放的谷氨酸是非囊泡来源的，可能来自内毛细胞和外毛细胞。