Tran Ba Huy Patrice, Lecain Eric
Service ORL, Hôpital Lariboisière, 2, rue Ambroise Paré, 75010 Paris et ESA 7060 CNRS.
Bull Acad Natl Med. 2002;186(7):1269-86; discussion 1286-8.
The secretory structures of the cochlea including stria vascularis and spiral ligament are responsible for the secretion of endolymph, a fluid characterized by a high potassium concentration [150-180 mM], a low sodium concentration [< 1 mM] and a positive potential [80-100 mV]. This intra-cellular-like fluid fills the endolymphatic compartment and is essential in the transduction process which takes place in the organ of Corti. Yet, the mechanisms which control the homeostasis of this fluid remain largely unknown. To approach this issue we investigated the possibility of a steroid synthesis by the rat cochlea which might modulate the secretion of endolymph. Results show that inner ear expresses mARN encoding some of the enzymes of the steroid pathways. We also investigated the presence of the gastric H+, K(+)-ATPase pump. Results from RT-PCR show that the gastric H+, K(+)-ATPase alpha and beta subunits are expressed in the rat inner ear-lateral wall, organ of Corti and spiral ganglion neurons. The presence of the alpha subunit in inner ear was confirmed by immunoblot. Immunohistochemistry localized this protein in the intermediate cells of the stria vascularis, in the spiral ligament and in spiral ganglion neurons. Along with the vacuolar H(+)-ATPase, the gastric H+, K(+)-ATPase could be involved in the maintenance of H+ equilibrium in endolymph. All these arguments suggest that among the various types of so-called "sensorineural" deafness, some entities including some forms of congenital hearing loss and diuretic-induced ototoxic deafness should be classified as endolymphatic deafness. Such identification seems necessary since these entities result from different pathogenetic mechanisms and might benefit from the development of new therapies.
耳蜗的分泌结构，包括血管纹和螺旋韧带，负责内淋巴的分泌。内淋巴是一种具有高钾浓度[150 - 180 mM]、低钠浓度[< 1 mM]和正电位[80 - 100 mV]的液体。这种类似细胞内的液体充满内淋巴腔，对柯蒂氏器中发生的转导过程至关重要。然而，控制这种液体稳态的机制在很大程度上仍不清楚。为了解决这个问题，我们研究了大鼠耳蜗进行类固醇合成以调节内淋巴分泌的可能性。结果表明，内耳表达编码类固醇途径中某些酶的mRNA。我们还研究了胃H⁺，K⁺-ATP酶泵的存在。RT-PCR结果显示，胃H⁺，K⁺-ATP酶α和β亚基在大鼠内耳侧壁、柯蒂氏器和螺旋神经节神经元中表达。通过免疫印迹证实了内耳中α亚基的存在。免疫组织化学将该蛋白定位在血管纹的中间细胞、螺旋韧带和螺旋神经节神经元中。与液泡H⁺-ATP酶一起，胃H⁺，K⁺-ATP酶可能参与维持内淋巴中的H⁺平衡。所有这些证据表明，在各种所谓的“感音神经性”耳聋中，一些类型，包括某些先天性听力损失和利尿剂诱导的耳毒性耳聋，应归类为内淋巴性耳聋。这种识别似乎是必要的，因为这些类型是由不同的致病机制引起的，可能会受益于新疗法的开发。
