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The analysis of the mechanism of osmoregulation in the inner ear.

内耳渗透压调节机制分析。

基本信息

批准号：
07671879
负责人：
MATSUNAGA Takashi
金额：
$ 1.41万
依托单位：
Nara Medical University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

We investigated the expression of sodium myo-inositol cotransporter (SMIT) mRNA in the inner ear and brain of rats by in situ hybridization method to understand the mechanism of the osmoreguration system mediated by osmolytes.In the cochlea, the most intense SMIT mRNA signals were observed in fibrocytes of the spiral ligament, moderate signals were found in the spiral limbus, inner hair cells and spiral ganglion cells, while the hybridization signals were almost undetectable in the marginal cells of the stria vascularis and outer hair cells. In the vestibular system, moderate hybridization signals were found in the sensory epithelium, fibrocytes and vestibular ganglion cells. These findings suggest that SMIT plays an important role in maintenance of intracellular ionic balance and cell volume in the inner ear, especially in the fibrocytes associated with generation of the ion gradients between the endolymph and perilymph.And we also investigated the changes in expressions of SMIT mRNA in the brain of acute hypernatremic rats by in situ hybridization and Northern blot methods. Under moderate acute hypernatremic conditions, SMIT mRNA level increased markedly at 1h and returned to almost control levels at 3h, in accordance with plasma Na^+ concentrations. Especially, distinct increase in SMIT mRNA expression were observed in the granule cells and glial cells in the cerebellum. The definite increases of SMIT mRNA expression was not seen in the chronic hypernatremic rats. These findings indicate that SMIT plays an important role in osmoregulation, especially in the early stages of acute hypernatremia in the brain.

为了探讨渗透调节剂介导的耳蜗复律系统的机制，我们采用原位杂交方法研究了SMIT mRNA在大鼠内耳和脑中的表达，结果发现，在耳蜗螺旋韧带的纤维细胞中SMIT mRNA表达最强，螺旋利姆布斯、内毛细胞和螺旋神经节细胞中也有中等强度的SMIT mRNA表达，而血管纹边缘细胞和外毛细胞几乎检测不到杂交信号。在前庭系统中，在感觉上皮、纤维细胞和前庭神经节细胞中发现中等杂交信号。结果表明，SMIT在维持内耳细胞内离子平衡和细胞体积中起重要作用，尤其是在纤维细胞中，与内、外淋巴液间离子梯度的产生有关。在中度急性高钠血症条件下，SMIT mRNA水平在1小时显著升高，3小时基本恢复到对照水平，与血浆Na^+浓度一致。特别是在小脑颗粒细胞和胶质细胞中SMIT mRNA表达明显增加。慢性高钠血症大鼠SMIT mRNA表达无明显增加。这些结果表明，SMIT在脑钠调节中起着重要作用，特别是在急性高钠血症的早期阶段。