Akiyama Kosuke, Miyashita Takenori, Matsubara Ai, Inamoto Ryuhei, Mori Terushige, Nishiyama Akira, Mori Nozomu
Department of Otolaryngology, Faculty of Medicine, Kagawa University, Kagawa 761-0793, Japan.
Acta Otolaryngol. 2010 Feb;130(2):228-32. doi: 10.3109/00016480903092357.
11beta-Hydroxysteroid dehydrogenase type 2 (11bHSD-2) enables aldosterone to bind to mineralocorticoid receptors (MRs) selectively by converting cortisol (corticosterone) into inactive metabolites. Its expression in the endolymphatic sac (ES) suggests that aldosterone may selectively act on the ES through its binding to MRs by the action of 11betaHSD-2, and supports the notion that ES is an aldosterone target organ. We propose that 11betaHSD-2 is a dominant isoform of 11betaHSDs in the ES, and the ES (especially the intermediate portion of the ES) may be the main aldosterone target in the inner ear.
The purpose of this study was to examine 11bHSD isoform expression in the rat inner ear, mainly 11betaHSD-2 in the ES.
In the ES and whole cochlea, 11betaHSDs were examined by RT-PCR using highly specific ES RNA by laser capture microdissection. In addition, 11betaHSD-2 localization in the rat ES was determined by immunohistochemistry.
RT-PCR demonstrated 11betaHSD-2 expressed in the rat ES. In addition, its localization was observed mainly in the intermediate portion and a faint immune positive signal was observed in other parts of the ES. In contrast, 11bHSD-1 was undetectable in the ES by RT-PCR. Both types of 11betaHSDs were expressed in rat cochlea.
2型11β-羟基类固醇脱氢酶（11βHSD-2）通过将皮质醇（皮质酮）转化为无活性代谢产物，使醛固酮能够选择性地与盐皮质激素受体（MRs）结合。其在内淋巴囊（ES）中的表达表明，醛固酮可能通过11βHSD-2的作用与MRs结合，从而选择性地作用于ES，并支持ES是醛固酮靶器官的观点。我们提出，11βHSD-2是ES中11βHSDs的主要亚型，并且ES（尤其是ES的中间部分）可能是内耳中醛固酮的主要靶器官。
本研究的目的是检测大鼠内耳中11βHSD亚型的表达，主要是ES中的11βHSD-2。
在内淋巴囊和整个耳蜗中，通过激光捕获显微切割技术使用高度特异性的ES RNA，采用逆转录聚合酶链反应（RT-PCR）检测11βHSDs。此外，通过免疫组织化学确定大鼠内淋巴囊中11βHSD-2的定位。
RT-PCR显示11βHSD-2在大鼠内淋巴囊中表达。此外，其定位主要在内淋巴囊的中间部分观察到，在内淋巴囊的其他部分观察到微弱的免疫阳性信号。相比之下，通过RT-PCR在内淋巴囊中未检测到11βHSD-1。两种类型的11βHSDs均在大鼠耳蜗中表达。
