Portier F, van den Abbeele T, Lecain E, Sauvaget E, Escoubet B, Huy P T, Herman P
Laboratoire d'Otologie Expérimentale, Faculté Lariboisière-St-Louis, Institut National de la Santé et de la Recherche Médicale Unité 426, Faculté Xavier Bichat, Université Paris VII, 75010 Paris, France.
Am J Physiol. 1999 Feb;276(2):C312-7. doi: 10.1152/ajpcell.1999.276.2.C312.
The physiology of the middle ear is primarily concerned with keeping the cavities air filled and fluid free to allow transmission of the sound vibrations from the eardrum to the inner ear. Middle ear epithelial cells are thought to play a key role in this process, since they actively transport Na+ and water. The PO2 of the middle ear cavities varies from 44 to 54 mmHg in healthy human ears but may be lower in the course of secretory otitis media. The effect of chronic hypoxia on ion transport was investigated on a middle ear cell line using the short-circuit current technique. Chronic hypoxia reversibly decreased the rate of Na+ absorption across the MESV cell line. Although a decrease in cellular ATP content was observed, the decrease of Na+ absorption seemed related to a primary modulation of apical Na+ entry. As revealed by RNase protection assay, the decrease in the rate of apical Na+ entry strictly paralleled the decrease in the expression of transcripts encoding the alpha-subunit of the epithelial Na+ channel. This effect of oxygen on Na+ absorption might account for 1) the presence of fluid in the middle ear in the course of secretory otitis media and 2) the beneficial effect of the ventilation tube in treating otitis media that allows the PO2 to rise and restores the fluid clearance.
中耳的生理功能主要涉及保持中耳腔充满空气且无液体，以使鼓膜的声音振动能够传递至内耳。中耳上皮细胞被认为在此过程中发挥关键作用，因为它们能主动转运钠离子和水。在健康人耳中，中耳腔的氧分压在44至54 mmHg之间变化，但在分泌性中耳炎病程中可能会更低。利用短路电流技术，在一种中耳细胞系上研究了慢性缺氧对离子转运的影响。慢性缺氧可使MESV细胞系的钠离子吸收速率可逆性降低。尽管观察到细胞内ATP含量减少，但钠离子吸收的降低似乎与顶端钠离子内流的原发性调节有关。核糖核酸酶保护试验显示，顶端钠离子内流速率的降低与编码上皮钠离子通道α亚基的转录本表达降低严格平行。氧对钠离子吸收的这种作用可能解释了：1）分泌性中耳炎病程中中耳内液体的存在；2）通气管在治疗中耳炎中的有益作用，通气管可使氧分压升高并恢复液体清除。
