Regulation of inner ear fluid in the rat by vasopressin

Kitano, Hiroya; Suzuki, Mikio; Kitanishi, Tsuyoshi; Yazawa, Yoshiro; Kitajima, Kazutomo; Isono, Takahiro; Takeda, Taizo; Kimura, Hiroshi; Tooyama, Ikuo

doi:10.1097/00001756-199904260-00009

Cited by 40 publications

(36 citation statements)

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“…Previous studies have shown that AQP2 protein and/or mRNA are expressed in the inner ear of rats. 19,39,46 Furthermore, the V2 receptor and/or its mRNA are found in the cochlea. 16,18 These previous studies suggest that water homeostasis in the inner ear is partly regulated via the VP-AQP2 system.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the following evidence has accumulated to suggest that VP is closely associated with the formation of EH: (1) plasma levels of arginine VP are higher in patients with MD and may depend on the phase that the patient is in, [9][10][11] (2) acute and chronic application of arginine VP produces EH in guinea-pigs and rats, [12][13][14] (3) V2 receptor mRNA is expressed in rat and human inner ear, [15][16][17][18] and (4) expression of V2 receptor mRNA in the rat inner ear is downregulated by VP application. 19 Such accumulated evidence has led to the assumption that production of endolymph is controlled by VP-AQP2 system.…”

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confidence: 99%

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Morphological and functional changes in a new animal model of Ménière's disease

Egami

Kakigi

Sakamoto

et al. 2013

Laboratory Investigation

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The purpose of this study was to clarify the underlying mechanism of vertiginous attacks in Ménière's disease (MD) while obtaining insight into water homeostasis in the inner ear using a new animal model. We conducted both histopathological and functional assessment of the vestibular system in the guinea-pig. In the first experiment, all animals were maintained 1 or 4 weeks after electrocauterization of the endolymphatic sac of the left ear and were given either saline or desmopressin (vasopressin type 2 receptor agonist). The temporal bones from both ears were harvested and the extent of endolymphatic hydrops was quantitatively assessed. In the second experiment, either 1 or 4 weeks after surgery, animals were assessed for balance disorders and nystagmus after the administration of saline or desmopressin. In the first experiment, the proportion of endolymphatic space in the cochlea and the saccule was significantly greater in ears that survived for 4 weeks after surgery and were given desmopressin compared with other groups. In the second experiment, all animals that underwent surgery and were given desmopressin showed spontaneous nystagmus and balance disorder, whereas all animals that had surgery but without desmopressin administration were asymptomatic. Our animal model induced severe endolymphatic hydrops in the cochlea and the saccule, and showed episodes of balance disorder along with spontaneous nystagmus. These findings suggest that administration of desmopressin can exacerbate endolymphatic hydrops because of acute V2 (vasopressin type 2 receptor)-mediated effects, and, when combined with endolymphathic sac dysfunction, can cause temporary vestibular abnormalities that are similar to the vertiginous attacks in patients with MD. Ménière's disease (MD) is a well-known inner ear disorder characterized by symptoms including recurring attacks of vertigo typically lasting for hours, fluctuating sensorineural hearing loss, and tinnitus. Since the milestone findings on the temporal bones of MD patients, 1,2 endolymphatic hydrops (EH) has been considered as the histopathological origin of MD, as characteristic morphological changes were reported to be produced by surgical obstruction of the endolymphatic sac (ES) in guinea-pig. 3 This observation indicates that malabsorption of endolymph in the ES is one of the possible mechanisms underlying the development of EH. This experimentally induced EH has been frequently used as an animal model to investigate the pathogenesis of inner ear disorders associated with EH. In terms of vestibular function, while canal dysfunction and/or spontaneous nystagmus have been occasionally observed in this animal model, 4,5 episodes of vertiginous attack or balance disorder have only rarely been observed. 6 In other words, this model is insufficient for fully representing the common symptoms of MD.Water homeostasis of the inner ear is essential for maintaining the functions of hearing and balance. EH is considered to be the result of disruption of inner ear water homeostasis, which ...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Morphological and functional changes in a new animal model of Ménière's disease

Egami

Kakigi

Sakamoto

et al. 2013

Laboratory Investigation

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“…We therefore sought to determine whether vasopressin can directly induce endolymphatic hydrops in the rat inner ear. In the previous study, we found that infusion of vasopressin induced a down-regulation of V2 AVP receptor mRNA in these cases [6]. These findings suggest that vasopressin directly regulates fluid levels in the inner ear, most likely by a down-regulation of its receptor.…”

Section: Discussionmentioning

confidence: 67%

“…The results of the assay of renal-type arginine vasopressin (V2-AVP) receptor mRNA by quantitative RT-PCR demonstrated a significantly lower level of this transcript in vasopressininfused rats than in saline-infused rats. The levels of CNP and ANP-B receptors mRNA, however, were the same in both groups of rats [6].…”

Section: Introductionmentioning

confidence: 79%

Endolymphatic Hydrops by Administration of Vasopressin in the Rat.

Kitano

Takeda²,

Takeda³

et al. 2001

Acta Histochem. Cytochem

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The anti-diuretic hormone, vasopressin, has been shown to be important in regulating inner ear fluid. We report on the involvement between Meniere's disease and vasopressin. We designed an experiment to determine whether vasopressin directly affects the fluid level. We chronically infused this hormone in rats and examined them for morphological signs of endolymphatic hydrops. Vasopressin infusion significantly increased the scala media area by 5.9r7.1% (P0.01), and the length of Reissner's membrane by 5.9r3.2% (P0.001). The results suggest that high plasma levels of vasopressin may be a principal causal factor of endolymphatic hydrops in Meniere's disease, perhaps due to down-regulating the number of vasopressin receptors.

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“…Sawada et al [13] and Beitz et al [9] have shown respectively AQP2 mRNA in the rat cochlea and endolymphatic sac with RT-PCR, a quantitative analysis but not a localization detection. Though all these data were based upon rat or mouse with some discrepancies, they suggest that AQP2 may play important roles in regulation of endolymph by vasopressin because vasopressin receptor in the inner ear has been identified [14,15], and regulation of AQP2 expression by vasopressin via their receptors and its affect on electrolytes metabolism has been well established in kidney [1,5].…”

Section: Discussionmentioning

confidence: 99%

Expression of Aquaporins in the Cochlea and Endolymphatic Sac of Guinea Pig

Zhong¹,

Liu²

2003

ORL

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It has been shown that the aquaporin (AQP) family forms membrane pores selectively permeable for water and some small solutes such as glycerol and urea, and thus plays important roles in regulating the fluid in many organs involved in fluid transport such as kidney, lung and brain. The aims of the present study were to investigate the cellular localization and its significance of aquaporins (AQPs) in various subregions of the cochlea and endolymphatic sac of guinea pig. The expression patterns of AQP1, 2, 3 and 4 were immunolabeled with the specific polyclonal rabbit antibodies against the rat AQP1, 2, 3 and 4. Our immunohistochemical examination showed that in the cochlea, AQP1, 3 and 4 were widely distributed in various locations including stria vascularis, spiral ligament, the organ of Corti and spiral ganglion in the similar patterns except that AQP3 in the stria vascularis was lightly weaker than AQP1 and AQP4. AQP2 was labeled only in Reissner’s membrane. In the endolymphatic sac, AQP1, AQP3 and AQP4 were strongly expressed in the epithelial cells and subepithelial cells similarly with the exception that AQP3 was lightly weaker than AQP1 and AQP4. No AQP2 immunoreactivity was detected in the endolymphatic sac. Theses results suggest that different members of the AQP family in the labyrinth may work in concert to regulate endolymph and to maintain homeostasis in the inner ear.

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Regulation of inner ear fluid in the rat by vasopressin

Cited by 40 publications

References 4 publications

Morphological and functional changes in a new animal model of Ménière's disease

Morphological and functional changes in a new animal model of Ménière's disease

Endolymphatic Hydrops by Administration of Vasopressin in the Rat.

Expression of Aquaporins in the Cochlea and Endolymphatic Sac of Guinea Pig

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