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Pan X, Huang C, Peng A, Zhang Z. Immunohistochemical localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac. J Laryngol Otol 2023; 137:1340-1344. [PMID: 36502818 DOI: 10.1017/s0022215122002444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE This study aimed to determine the distribution and subcellular localisation of aquaporin 2 and vasopressin type 2 receptor in the human endolymphatic sac. METHODS Ten samples of human endolymphatic sac were collected during acoustic neurinoma removal using the translabyrinthine approach. Immunohistochemistry and immunofluorescence were performed using aquaporin 2 and vasopressin type 2 receptor monoclonal antibodies. RESULTS Confocal microscopy demonstrated that vasopressin type 2 receptor labelling was expressed in both the apical and basolateral plasma membranes, and in the cytoplasm of the endolymphatic sac epithelium, whereas aquaporin 2 was strongly expressed at the basolateral site of the endolymphatic sac epithelium, in both the intraosseous and extraosseous parts of the endolymphatic sac. CONCLUSION Both aquaporin 2 and vasopressin type 2 receptor were detected in the epithelial cells of the human endolymphatic sac, suggesting that this channel may be involved in inner-ear fluid homeostasis. However, strong basolateral expression of aquaporin 2 in endolymphatic sac epithelium suggested that the function of aquaporin 2 may differ between the endolymphatic sac and kidney.
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Affiliation(s)
- X Pan
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - C Huang
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - A Peng
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Z Zhang
- Department of Otolaryngology - Head and Neck Surgery, Second Xiangya Hospital, Central South University, Changsha, Hunan, China
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Asmar MH, Gaboury L, Saliba I. Ménière’s Disease Pathophysiology: Endolymphatic Sac Immunohistochemical Study of Aquaporin-2, V2R Vasopressin Receptor, NKCC2, and TRPV4. Otolaryngol Head Neck Surg 2018; 158:721-728. [DOI: 10.1177/0194599818756829] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Objectives Endolymphatic sac (ELS) pathophysiology in Ménière’s disease (MD) remains poorly understood. We identified from the literature a group of proteins expressed on the ELS and involved in endolymph volume regulation: aquaporin-2 (AQP2), vasopressin receptor V2R, sodium potassium chloride cotransporter 2 (NKCC2), and transient receptor potential cation channel V4 (TRPV4). Our objective was to determine whether their ELS expression was altered in MD, to better understand the pathophysiology of endolymphatic hydrops. Study Design Prospective case-control study. Setting Tertiary care center. Subjects Twenty-four patients with definite MD undergoing endolymphatic duct blockage surgery were recruited, as well as 23 controls with no history of MD undergoing surgery for vestibular schwannoma (VS). Methods ELS biopsies and blood samples for plasma arginine vasopressin (AVP) were obtained. Immunohistochemistry for AQP2, V2R, NKCC2, and TRPV4 was performed. Slides were scanned digitally for highly sensitive pixel density analysis by specialized software (VIS; Visiopharm). Results Global scores generated by the software represent total and relative protein expression density of 3 staining intensity levels, exclusively on ELS epithelium. AQP2 expression density was significantly elevated in MD compared to VS ( P = .003). There was no significant difference in plasma AVP, V2R, NKCC2, and TRPV4 expression. Conclusion This original study evaluates simultaneous in situ expression of AQP2, V2R, NKCC2, and TRPV4 on the human ELS in MD, with a control group. Our results show only AQP2 upregulation on the ELS of patients with MD. We suggest a constitutively increased expression of AQP2 in MD, independent of its regulatory axis (AVP-V2R). Acquired regulator sequence mutations could support this model.
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Affiliation(s)
- Marc-Henri Asmar
- University of Montreal Hospital Centre Research Centre (CRCHUM), Montreal, QC, Canada
| | - Louis Gaboury
- University of Montreal Hospital Centre Research Centre (CRCHUM), Montreal, QC, Canada
- Department of Pathology and Cell Biology, University of Montreal Hospital Centre (CHUM), Montreal, QC, Canada
| | - Issam Saliba
- University of Montreal Hospital Centre Research Centre (CRCHUM), Montreal, QC, Canada
- Division of Otolaryngology–Head & Neck Surgery, University of Montreal Hospital Centre (CHUM), Montreal, QC, Canada
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Runggaldier D, Pradas LG, Neckel PH, Mack AF, Hirt B, Gleiser C. Claudin expression in the rat endolymphatic duct and sac - first insights into regulation of the paracellular barrier by vasopressin. Sci Rep 2017; 7:45482. [PMID: 28374851 PMCID: PMC5379655 DOI: 10.1038/srep45482] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 02/28/2017] [Indexed: 12/13/2022] Open
Abstract
Hearing and balance functions of the inner ear rely on the homeostasis of the endolymphatic fluid. When disturbed, pathologic endolymphatic hydrops evolves as observed in Menière’s disease. The molecular basis of inner ear fluid regulation across the endolymphatic epithelium is largely unknown. In this study we identified the specific expression of the tight junction (TJ) molecules Claudin 3, 4, 6, 7, 8, 10, and 16 in epithelial preparations of the rat inner ear endolymphatic duct (ED) and endolymphatic sac (ES) by high-throughput qPCR and immunofluorescence confocal microscopy. Further we showed that Claudin 4 in the ES is a target of arginine-vasopressin (AVP), a hormone elevated in Menière’s disease. Moreover, our transmission-electron microscopy (TEM) analysis revealed that the TJs of the ED were shallow and shorter compared to the TJ of the ES indicating facilitation of a paracellular fluid transport across the ED epithelium. The significant differences in the subcellular localization of the barrier-forming protein Claudin 3 between the ED and ES epithelium further support the TEM observations. Our results indicate a high relevance of Claudin 3 and Claudin 4 as important paracellular barrier molecules in the ED and ES epithelium with potential involvement in the pathophysiology of Menière’s disease.
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Affiliation(s)
- Daniel Runggaldier
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Lidia Garcia Pradas
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Peter H Neckel
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Andreas F Mack
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Bernhard Hirt
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
| | - Corinna Gleiser
- Institute of Clinical Anatomy and Cell Analysis, University of Tübingen, Tübingen, Germany
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Morphological and functional changes in a new animal model of Ménière's disease. J Transl Med 2013; 93:1001-11. [PMID: 23877650 DOI: 10.1038/labinvest.2013.91] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/20/2013] [Accepted: 06/22/2013] [Indexed: 11/09/2022] Open
Abstract
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.
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Water channel proteins in the inner ear and their link to hearing impairment and deafness. Mol Aspects Med 2012; 33:612-37. [DOI: 10.1016/j.mam.2012.06.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 06/11/2012] [Accepted: 06/17/2012] [Indexed: 11/24/2022]
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Nishioka R, Takeda T, Kakigi A, Okada T, Takebayashi S, Taguchi D, Nishimura M, Hyodo M. Expression of aquaporins and vasopressin type 2 receptor in the stria vascularis of the cochlea. Hear Res 2010; 260:11-9. [DOI: 10.1016/j.heares.2009.09.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Revised: 09/21/2009] [Accepted: 09/23/2009] [Indexed: 10/20/2022]
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Nishimura M, Kakigi A, Takeda T, Okada T, Doi K. Time course changes of vasopressin-induced enlargement of the rat intrastrial space and the effects of a vasopressin type 2 antagonist. Acta Otolaryngol 2009; 129:709-15. [PMID: 18836965 DOI: 10.1080/00016480802419115] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
CONCLUSION The intrastrial space was enlarged remarkably at 20 min after vasopressin (VP) injection, and this enlargement of the intrastrial space was reduced by administration of OPC-31260 before VP injection. These results suggest that VP increases the influx of water from the perlymph to the basal cells via aquaporin (AQP) 2 and causes the formation of endolymphatic hydrops. OBJECTIVES To investigate a time course of changes of the stria vascularis after VP injection and the influence of OPC-31260 on experimentally induced enlargement of the intrastrial space caused by VP injection. MATERIALS AND METHODS In the time course study, Wistar rats were injected with 50 microg/kg of VP subcutaneously. The stria vascularis specimens were harvested at 10, 20, 30, and 60 min after VP injection. For OPC-31260 administration, animals were administered 100 mg/kg of OPC-31260 orally 1 h before receiving 50 microg/kg of VP subcutaneously. The specimens were harvested 20 min after VP injection. These specimens were observed using transmission electron microscopy. RESULTS In the time course study, the incidence of intrastrial space enlargement was 50%, 100%, 25%, and 0% for 10, 20, 30, and 60 min, respectively. In the study with OPC-31260 administration, the stria vascularis showed no morphological changes.
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Abstract
The homeostasis of water in the inner ear is essential for maintaining function of hearing and equilibrium. Since the discovery of aquaporin water channels, it has become clear that these channels play a crucial role in inner ear fluid homeostasis. Indeed, proteins or mRNAs of AQP1, AQP2, AQP3, AQP4, AQP5, AQP6, AQP7 and AQP9 are expressed in the inner ear. Many of them are expressed mainly in the stria vascularis and the endolymphatic sac, which are the main sites of secretion and/or absorption of endolymph. Vasopressin type2 receptor is also expressed there. Water homeostasis of the inner ear is regulated in part via the arginine vasopressin-AQP2 system in the same fashion as in the kidney, and endolymphatic hydrops, a morphological characteristic of Meniere's disease, is thought to be caused by mal-regulation of this system. Therefore, aquaporins appear to be important for the development of novel drug therapies for Meniere's disease and related disorders.
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Taguchi D, Takeda T, Kakigi A, Okada T, Nishioka R, Kitano H. Expression and immunolocalization of aquaporin-6 (Aqp6) in the rat inner ear. Acta Otolaryngol 2008; 128:832-40. [PMID: 18607959 DOI: 10.1080/00016480701765691] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
CONCLUSION Since aquaporin-6 (Aqp6) protein was located in the membrane of intracellular vesicles of the stria vascularis, endolymphatic sac, and vestibule, Aqp6 might be involved in some distinct physiological function of acid-base metabolism and water balance in endolymphatic fluid homeostasis. However, its lack of expression on the plasma membrane indicates that Aqp6 does not have a direct role in water flux via the plasma membrane. OBJECTIVE To evaluate the expression and immunolocalization of Aqp6 in the rat inner ear. MATERIALS AND METHODS Wistar rats were used. Aqp6 mRNA expression in the rat inner ear was investigated in the vestibulum as well as in the cochlea and endolymphatic sac using the reverse transcription-polymerase chain reaction (RT-PCR) method, and detailed immunolocalization of Aqp6 in the rat inner ear was investigated using immunohistochemical methods including immunofluorescence microscopy and immunoelectron microscopy. RESULTS We obtained novel data showing that not just Aqp6 mRNA but also Aqp6 protein is expressed in the cochlea, endolymphatic sac, and vestibule. Immunoelectron microscopic studies revealed that the immunolabelled gold was diffusely seen in the intracellular area of the stria vascularis, endolymphatic sac, and vestibule, but never in the plasma membranes.
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Kakigi A, Nishimura M, Takeda T, Taguchi D, Nishioka R. Expression of aquaporin1, 3, and 4, NKCC1, and NKCC2 in the human endolymphatic sac. Auris Nasus Larynx 2008; 36:135-9. [PMID: 18606512 DOI: 10.1016/j.anl.2008.04.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 03/21/2008] [Accepted: 04/13/2008] [Indexed: 10/21/2022]
Abstract
OBJECTIVE To locate aquaporin (AQP) 1, 3, and 4, Na-K-2Cl cotransporter (NKCC) 1 and 2 in the human endolymphatic sac (ES). METHODS A sample of human ES was harvested during the removal of vestibular schwannoma via the translabyrinthine approach. The sample was immediately fixed in 4% paraformaldehyde and embedded in OCT compound. Immunohistochemistry was performed with AQP1, 3, and 4, NKCC1, and NKCC2 polyclonal antibodies. RESULTS AQP1, AQP3, and NKCC2 were strongly expressed in the epithelial layer of the ES. AQP4 and NKCC1 were weakly expressed in the epithelial layer of the ES. CONCLUSIONS As it is impossible to perform quantitative analysis based on the fluorescence intensity of each immunoreactivity, we have presented the existence of AQP1, 3, and 4, NKCC1, and NKCC2 in the ES. The expression of NKCC1 and 2 indicated that the ES may have both secretory and adsorptive functions to maintain the homeostasis of endolymph.
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Affiliation(s)
- Akinobu Kakigi
- Department of Otolaryngology, Kochi Medical School, Nankoku, Japan.
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Abstract
INTRODUCTION The aim of this research was to describe nomograms of brainstem auditory evoked potentials, oscillating stimulation of the vestibular organs and ultrastructural research methodology of a spiral organ of guinea-pigs. MATERIALS AND METHODS For the experimental purposes 60 guinea-pigs of both sexes, weight 250-300 grams, were used as research materials. After general anesthesia with Ketalar dosed 100 milligrams per kilogram and with Fentanyl dosed 0.1 milliliter per kilogram of the body mass, brainstem auditory evoked potentials were registered and the oscillating chair test (no prior anesthesia). Was placed on an assistant's knees, who was sitting on a chair. Then the guinea-pigs were anesthetized with 35 per cent solution of chloral hydrate intraperitoneally (dosed 1 milliliter per kilogram of the body mass). For electron microscopic research membranous helix was collected bilaterally by the method of micropreparation. Qualitative observation was conducted in the Philips' electron microscope (EM 300). RESULTS On the basis of the obtained results it was concluded that the time of transmission between elements P1-P2 is constant and figures between 3.1 and 3.6 ms independently from a force of stimulation. Vestibular organs of a guinea-pig are more sensitive to high accelerations (17-12 degree/s2) than human vestibularl organs. However, their reaction is much weaker to lower accelerations (12-0 degree/s2). CONCLUSIONS The processed nomograms of the brainstem auditory evoked potentials, oscillating stimulation of vestibular organs and methodology of ultrastructural research in guinea-pigs' spiral organs are expected to facilitate using them in experimental research.
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Affiliation(s)
- Jurek Olszewski
- Klinika Otolaryngologii i Onkologii Laryngologicznej II Katedry Otolaryngologii UM w Lodzi.
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Gaal V, Mark L, Kiss P, Kustos I, Tamas A, Kocsis B, Lubics A, Nemeth V, Nemeth A, Lujber L, Pytel J, Toth G, Reglodi D. Investigation of the effects of PACAP on the composition of tear and endolymph proteins. J Mol Neurosci 2008; 36:321-9. [PMID: 18421426 DOI: 10.1007/s12031-008-9067-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 03/12/2008] [Indexed: 12/30/2022]
Abstract
Pituitary adenylate cyclase activating polypeptide (PACAP) is widely distributed in ocular tissues, including the lacrimal gland. PACAP has been shown to influence the activity of several exocrine glands, but its effects on the composition of the tear film are not known yet. Similarly, the presence of PACAP has already been shown in the inner ear, but it is not known whether PACAP influences the composition of the endolymph. The aim of the present study was to investigate whether systemic injection of PACAP has any modulatory effects on the protein composition of the tear film and endolymph using chip electrophoresis and mass spectrometry analysis. Tear and endolymph samples were collected from rats and chickens, respectively, at various time points after systemic injection of PACAP. Fluid samples were further processed for chip electrophoretic studies. No difference was found in the protein composition of the endolymph between control and PACAP-treated animals. In contrast, tear samples showed a marked difference after PACAP treatment. Proteins in the molecular range 50-70 kDa, which showed a different chip electropherogram profile in every PACAP-treated sample, were further analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. PACAP treatment induced a repression in certain keratins, while others were induced after PACAP injection. Furthermore, PACAP treatment decreased aldehyde dehydrogenase expression. The present study provides a base for further studies on the in vivo effects of PACAP on the composition of tear film. These investigations may have important clinical relevance because of the noninvasive sample collection, the correlation between tear proteins and ocular diseases, and the possible presence of biomarkers for both ophthalmological and systemic pathological conditions.
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Affiliation(s)
- Valeria Gaal
- Department of Ophthalmology, University of Pecs, Ifjusag u 13, 7624, Pecs, Hungary
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Taguchi D, Takeda T, Kakigi A, Takumida M, Nishioka R, Kitano H. Expressions of Aquaporin-2, Vasopressin Type 2 Receptor, Transient Receptor Potential Channel Vanilloid (TRPV)1, and TRPV4 in the Human Endolymphatic Sac. Laryngoscope 2007; 117:695-8. [PMID: 17415141 DOI: 10.1097/mlg.0b013e318031c802] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVE To localize aquaporin (AQP)2, vasopressin type 2 receptor (V2-R), and transient receptor potential channel vanilloid subfamily 1, 4 (TRPV1, TRPV4) in the human endolymphatic sac (ES). METHODS Three samples of human ES were sampled during the removal of vestibular schwannoma by way of the translabyrinthine approach. The samples were immediately fixed in 4% paraformaldehyde and embedded in OCT compound; immunohistochemistry was performed with AQP2, V2-R, TRPV1, and TRPV4 polyclonal antibodies. RESULTS AQP2, V2-R, TRPV1, and TRPV4 proteins were detected in the epithelial layer of the ES but were not observed in connective tissue around the ES. TRPV1 was also expressed in blood vascular endothelial cells of the connective tissue of ES. CONCLUSIONS AQP2, V2-R, and TRPV4 were expressed in the luminal epithelium of human ES. The same characteristic distribution of water and ion channels is seen in the kidney, where a significant amount of fluid is filtrated and resorbed. ES probably plays an active role in the homeostasis of the endolymph.
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Affiliation(s)
- Daizo Taguchi
- Department of Otolaryngology, Kochi Medical School, Nankoku, Kochi, Japan.
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Abstract
PURPOSE OF REVIEW Review of the role of aquaporins in inner ear homeostasis and potential role in the pathogenesis of Meniere's disease. RECENT FINDINGS Recent findings include the immunolocalization of aquaporins in the inner ear of mouse, rat, and human to cell types that are likely to undergo high ionic perturbances (e.g. potassium flux) and to putative areas of endolymph resorption or cycling. SUMMARY The expression of aquaporins and related proteins in the human cochlea and vestibular periphery resembles the distribution found in animal models, suggesting a critical role of aquaporins in inner ear water homeostasis and their potential role in the pathogenesis of Meniere's disease.
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Affiliation(s)
- Gail Ishiyama
- Department of Neurology, Division of Head and Neck Surgery, David Geffen School of Medicine at the University of California, Los Angeles 90095, USA.
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Takeda T, Takeda S, Kakigi A, Okada T, Nishioka R, Taguchi D. A comparison of dehydration effects of V2-antagonist (OPC-31260) on the inner ear between systemic and round window applications. Hear Res 2006; 218:89-97. [PMID: 16781097 DOI: 10.1016/j.heares.2006.05.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/16/2005] [Revised: 04/28/2006] [Accepted: 05/01/2006] [Indexed: 10/24/2022]
Abstract
V2-antagonist (OPC-31260 (OPC)) application to the scala tympani reduced endolymphatic hydrops. In the present study, we investigated whether systemic administration or local infusion via the round window (RW application) of OPC would be more suitable for clinical use. In Experiment 1, the increase ratios of the cross-sectional area of the scala media of experimentally induced endolymphatic hydrops were quantitatively assessed among four groups of non-OPC application, RW application of xanthan gum, systemic application of OPC and RW application of OPC. In Experiment 2, the effects of systemic and RW applications of OPC on plasma vasopressin (p-VP) concentrations and plasma osmolality (p-OSM) were investigated. In Experiment 3, endocochlear DC potential (EP) was measured in guinea pigs with the RW application of OPC. Electron microscopic observations of the stria vascularis and the hair cells were also made. Both systemic and RW applications of OPC significantly reduced endolymphatic hydrops. However, systemic application resulted in the distension of the Reissner's membrane in the non-operated ear, which seemed to be caused by elevated p-VP levels resulting from the systemic application of OPC. In contrast, RW application of OPC produced no apparent toxic effects in the inner ear, as indicated electrophysiological or morphological changes. Thus, drug delivery via the round window is more useful for the clinical application of OPC for medical decompression.
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Affiliation(s)
- Taizo Takeda
- Department of Otolaryngology, Kochi Medical School, Kohasu, Kochi 783-8505, Japan.
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