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Hsu CJ, Chen YS, Shau WY, Yeh TH, Lee SY, Lin-Shiau SY. Impact of Activities OF NA+,K+-Atpase and CA2+-Atpase in the Cochlear Lateral Wall on Recovery from Noise-Induced Temporary Threshold Shift. Ann Otol Rhinol Laryngol 2016; 111:842-9. [PMID: 12296342 DOI: 10.1177/000348940211100915] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The present study was designed to investigate the relationship between the noise-induced temporary threshold shift (TTS) and the specific activities of sodium potassium adenosine triphosphatase (Na+,K+-ATPase) and calcium adenosine triphosphatase (Ca2+-ATPase) in the cochlear lateral wall. The specific activities of these enzymes were quantified by microcolorimetric assay. Changes in auditory brain stem response (ABR) thresholds were compared with the quantitative alterations of the specific activities of Na+,K+-ATPase and Ca2+-ATPase in the cochlear lateral wall of guinea pigs with a noise-induced TTS. In the majority of those noise-exposed ears with complete recovery of ABR thresholds, the specific activities of both enzymes returned to at least 70% of the mean specific activity of the control group. Although other factors may be involved, reversible inactivation of Na+,K+-ATPase and Ca2+-ATPase in the cochlear lateral wall may be one component of the TTS. Our present findings could drive further studies on the molecular basis of noise-induced hearing loss.
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Affiliation(s)
- Chuan-Jen Hsu
- Department of Otolaryngology, National Taiwan University Hospital, Taipei, Republic of China
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Lo WC, Liao LJ, Wang CT, Young YH, Chang YL, Cheng PW. Dose-dependent effects of d-methionine for rescuing noise-induced permanent threshold shift in guinea-pigs. Neuroscience 2013; 254:222-9. [DOI: 10.1016/j.neuroscience.2013.09.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 09/01/2013] [Accepted: 09/12/2013] [Indexed: 11/29/2022]
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Mori Y, Watanabe M, Inui T, Nimura Y, Araki M, Miyamoto M, Takenaka H, Kubota T. Ca(2+) regulation of endocochlear potential in marginal cells. J Physiol Sci 2009; 59:355-65. [PMID: 19504169 PMCID: PMC10717738 DOI: 10.1007/s12576-009-0043-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2008] [Accepted: 05/02/2009] [Indexed: 11/26/2022]
Abstract
We examined the effect of the cytosolic Ca(2+) concentration ([Ca(2+)](c)) in marginal cells on the asphyxia- or furosemide-induced decrease in the endocochlear potential (EP) by perfusing the endolymph with or without a Ca(2+) chelator or inhibitors of Ca(2+)-permeable channels or Ca(2+)-pump during transient asphyxia or intravenous administration of furosemide. We obtained the following results. (1) Endolymphatic administration of SKF96365 (an inhibitor of TRPC and L-type Ca(2+) channels) or EGTA-acetoxymethyl ester (EGTA-AM) significantly inhibited both the transient asphyxia-induced decrease in EP (TAID) and the furosemide-induced decrease in EP (FUID). (2) Endolymphatic perfusion with nifedipine significantly inhibited the TAID but not the FUID. (3) The recovery from the FUID was significantly suppressed by perfusing the endolymph with EGTA-AM, nifedipine, or SKF96365. (4) Endolymphatic administration of thapsigargin inhibited both the FUID and TAID. (5) The recovery rate from the FUID was much slower than that from the TAID, indicating that furosemide may inhibit the Ca(2+)-pump. (6) A strong reaction in immunohistochemical staining for TRPC channels was observed in the luminal and basolateral membranes of marginal cells. (7) A positive staining reaction for the gamma subunit of epithelial Na(+) channels was observed in the luminal and basolateral membranes of marginal cells. (8) Positive EP was diminished toward 0 mV by the endolymphatic perfusion with 10 muM amiloride or 10 muM phenamil. Taken together, these findings suggest that [Ca(2+)](c) regulated by endoplasmic Ca(2+)-pump and Ca(2+)-permeable channels in marginal cells may regulate the positive EP, which is partly produced by the diffusion potential of Na(+) across the basolateral membrane in marginal cells.
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Affiliation(s)
- Yoshiaki Mori
- Department of Physiology II, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, Osaka, 569-8686 Japan
| | - Masahito Watanabe
- Department of Anatomy and Cell Biology, Osaka Medical College, Takatsuki, Osaka, 569-8686 Japan
| | - Takaki Inui
- Department of Otolaryngology, Osaka Medical College, Takatsuki, Osaka, 569-8686 Japan
| | - Yoshitsugu Nimura
- Department of Otolaryngology, Osaka Medical College, Takatsuki, Osaka, 569-8686 Japan
| | - Michitoshi Araki
- Department of Otolaryngology, Osaka Medical College, Takatsuki, Osaka, 569-8686 Japan
| | - Manabu Miyamoto
- Department of Physiology II, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, Osaka, 569-8686 Japan
| | - Hiroshi Takenaka
- Department of Otolaryngology, Osaka Medical College, Takatsuki, Osaka, 569-8686 Japan
| | - Takahiro Kubota
- Department of Physiology II, Osaka Medical College, 2-7 Daigakumachi, Takatsuki, Osaka, 569-8686 Japan
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Protection from noise-induced temporary threshold shift by D-methionine is associated with preservation of ATPase activities. Ear Hear 2008; 29:65-75. [PMID: 18091106 DOI: 10.1097/aud.0b013e31815d635b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE The present study was designed to test whether noise-induced temporary threshold shift (TTS) could be attenuated by D-methionine and its possible relation to the biochemical changes of cochlear lateral walls such as ATPase activities and oxidative stress in guinea pigs. DESIGN Thirty-two normal-hearing male guinea pigs were randomly divided into saline-treated and D-methionine-treated (300 mg/kg) experimental groups. One hour after treatment, they were exposed to a continuous broadband white noise at 105 +/- 2 dB sound pressure level for 10 min, causing TTS. Each group was then divided into four subgroups based on the number of survival days after noise exposure (0, 1, 2, and 7 days). Each subgroup had four animals and eight ears included. By means of click-evoked auditory brain stem responses (ABR), auditory thresholds of guinea pigs were measured before noise exposure, immediately after noise exposure, and before killing. After animals were killed, cochlear lateral walls were immediately harvested and assayed for enzyme-specific activities of Na+, K+-ATPase and Ca2+-ATPase, lipid peroxidation, and nitric oxide. RESULTS A 15.31 +/- 3.80 dB threshold shift was found immediately after noise exposure in saline-pretreated guinea pigs. In contrast, ABR threshold shift was significantly attenuated to 4.06 +/- 2.35 dB in D-methionine-treated animals. Furthermore, D-methionine enhanced the restoration of ABR threshold to baseline level by 1 day. In addition, noise significantly decreased Na+, K+-ATPase, and Ca2+-ATPase activities and increased lipid peroxidation and nitric oxide levels of the cochlear lateral walls. D-methionine significantly protected against all of these changes. CONCLUSIONS Noise not only induced TTS but also inhibited ATPase activities as well as increased oxidative stress in guinea-pig cochlear lateral walls; all of these changes could be attenuated by d-methionine through its antioxidative property. These results suggest the potential usefulness of d-methionine in protecting from noise-induced ototoxicity.
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Inui T, Mori Y, Watanabe M, Takamaki A, Yamaji J, Sohma Y, Yoshida R, Takenaka H, Kubota T. Physiological Role of L-Type Ca2+ Channels in Marginal Cells in the Stria Vascularis of Guinea Pigs. J Physiol Sci 2007; 57:287-98. [DOI: 10.2170/physiolsci.rp006807] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Accepted: 10/25/2007] [Indexed: 11/05/2022]
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Cheng PW, Liu SH, Hsu CJ, Lin-Shiau SY. Correlation of increased activities of Na+, K+-ATPase and Ca2+-ATPase with the reversal of cisplatin ototoxicity induced by d-methionine in guinea pigs. Hear Res 2005; 205:102-9. [PMID: 15953519 DOI: 10.1016/j.heares.2005.03.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2005] [Accepted: 03/08/2005] [Indexed: 11/23/2022]
Abstract
Na(+), K(+)-ATPase and Ca(2+)-ATPase in the cochlear lateral wall play an important role in maintaining ionic homeostasis and physiologic function of the cochlea. The present study was designed to test whether the changes of Na(+), K(+)-ATPase and Ca(2+)-ATPase activities of the cochlear lateral wall and the brainstem of guinea pigs after receiving cisplatin for seven consecutive days were correlated with the altered auditory brainstem responses (ABR). Furthermore, whether a chemoprotective agent, D-methionine reversed the increased ABR threshold induced by cisplatin accompanied with the increased ATPase activities was also evaluated. The results obtained showed that cisplatin exposure caused not only a significant increase of threshold but also altered various absolute wave and interwave latencies of ABR. In addition, cisplatin significantly decreased the Na(+), K(+)-ATPase and Ca(2+)-ATPase activities in the cochlear lateral wall with a good dose-response relationship. Regression analysis indicated that an increase of ABR threshold was well correlated with a decrease of both Na(+), K(+)-ATPase and Ca(2+)-ATPase activities in the cochlear lateral wall. A chemoprotectant, D-methionine indeed reversed both abnormalities of ABR and ATPase activities in a well correlation function. The selectivity of these observed changes induced by cisplatin and D-methionine was revealed by the findings that cisplatin-treated guinea pigs had normal III-V interwave latency of ABR and no reduction of Na(+), K(+)-ATPase and Ca(2+)-ATPase specific activities in the brainstem, which is in accordance with the nonpenetrable cisplatin across the blood brain barrier. Taken all together, the present findings suggest that biochemical damage and ionic disturbance may contribute to cisplatin-induced ototoxicity to some extent, which can be reversed by d-methionine.
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Affiliation(s)
- Po-Wen Cheng
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan
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Mineharu A, Mori Y, Nimura Y, Takamaki A, Araki M, Yamaji J, Yoshida R, Takenaka H, Kubota T. Endolymphatic Perfusion with EGTA-Acetoxymethyl Ester Inhibits Asphyxia- and Furosemide-Induced Decrease in Endocochlear Potential in Guinea Pigs. ACTA ACUST UNITED AC 2005; 55:53-60. [PMID: 15796789 DOI: 10.2170/jjphysiol.r2086] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We examined the effect of the Ca(2+) concentration in the endolymph ([Ca](e)) or in the endolymphatic surface cells ([Ca](i)) on the endocochlear potential (EP) by using an endolymphatic or perilymphatic perfusion technique, respectively. (i) A large increase in [Ca](e) up to approximately 10(-3) M with a fall in the EP was induced by transient asphyxia ( approximately 2 min) or by the intravenous administration of furosemide (60 mg/kg), and a significant correlation was obtained between the EP and p[Ca](e) (= -log [Ca](e), r = 0.998). (ii) Perfusion of the endolymph with 10 mM EGTA for 5 min neither produced any significant change in the EP nor altered the asphyxia-induced change in EP (DeltaEP(asp)), suggesting that neither [Ca](e) nor the Ca(2+) concentration gradient across the stria vascularis contributed directly to the generation of the EP in the condition of low [Ca](e). In contrast, endolymphatic perfusion with high Ca(2+) (more than 10 mM) produced a decrease in EP and a significant correlation was obtained between the EP and the Ca(2+) concentration of perfusion solution (r = 0.982), suggesting that Ca(2+) permeability may exist across the stria vascularis. (iii) The administration of a Ca(2+) chelator, EGTA-acetoxymethyl ester (AM, 0.3 mM), to the endolymph, which produced a gradual increase in EP, suppressed significantly, by 60-80%, DeltaEP(asp) or furosemide-induced changes in EP. In contrast, perilymphatic administration of 0.5 mM EGTA-AM caused no significant suppression of the DeltaEP(asp). These findings suggest that [Ca](i) plays an important role in generating/maintaining a large positive EP.
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Affiliation(s)
- Akihito Mineharu
- Department of Physiology II and Department of Otolaryngology, Osaka Medical College, Takatsuki, Osaka, 569-8686 Japan
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Terunuma T, Kawauchi S, Kajihara M, Takahashi S, Hara A. Effect of acoustic stress on glucocorticoid receptor mRNA in the cochlea of the guinea pig. ACTA ACUST UNITED AC 2003; 120:65-72. [PMID: 14667579 DOI: 10.1016/j.molbrainres.2003.10.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
As a first step toward elucidating the mechanism underlying the therapeutic effect of glucocorticoids on acute noise-induced hearing loss, we used semiquantitative reverse transcription polymerase chain reaction to study the level of glucocorticoid receptor (GR) mRNA in the cochlea of the guinea pig after acoustic overstimulation. The cochleas were dissected and divided into three portions (lateral portion, medial portion and modiolus). In the lateral portion, the glucocorticoid receptor mRNA level was significantly decreased 2 h after exposure to a 120 dB SPL sound and both 2 and 6 h after exposure to a 130 dB SPL sound. To determine where in the cochlea the changes in glucocorticoid receptor mRNA levels occur, in situ hybridization histochemistry was performed with digoxigenin-labeled sense and antisense RNA probes complementary to guinea pig glucocorticoid receptor mRNA. Glucocorticoid receptor mRNA was demonstrated in the spiral ligament, stria vascularis, spiral limbus and spiral ganglion. Moreover, the glucocorticoid receptor mRNA level was decreased in the spiral ligament, especially in the spiral prominence of the basal turn, 2 h after exposure to the 130 dB SPL sound. These results could imply that the therapeutic effect of glucocorticoids in the cochlea might be mediated in the spiral ligament, particularly in the spiral prominence.
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Affiliation(s)
- Tsumoru Terunuma
- Department of Otolaryngology, Institute of Clinical Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8575, Japan.
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Abstract
Thapsigargin, a drug that inhibits sarco-endoplasmic reticulum Ca(2+) ATPases (SERCAs), was infused into the perilymph compartment of the guinea pig cochlea in increasing concentrations (0.1-10 microM) while sound evoked cochlear potentials were monitored. Thapsigargin significantly suppressed the compound action potential of the auditory nerve, cochlear microphonics, and increased N(1) latency at low (56 dB SPL) and high intensity (92 dB SPL) levels of sound, suppressed low intensity sound evoked summating potential (SP) and greatly increased the magnitude of the high intensity sound evoked SP. At 10 microM, the drug suppressed the cubic distortion product otoacoustic emissions (2f(1)-f(2)=8 kHz, f(2)=12 kHz) evoked by both high and low intensity primaries (45, 60, 70 dB SPL). Thapsigargin (10 microM; 30 min) increased the endocochlear potential slightly (5 mV). In chronic animals, thapsigargin (10 microM; 60 min) destroyed many outer hair cells and some inner hair cells, especially in the basal turns. These effects are consistent with the hypothesis that the inhibition of the SERCAs affects the function of the cochlear amplifier and outer hair cells to a greater degree than it affects other functions of the cochlea.
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Affiliation(s)
- Richard P Bobbin
- Kresge Hearing Research Laboratory, Department of Otorhinolaryngology and Biocommunication, Louisiana State University Health Sciences Center, 533 Bolivar Street, 5th Floor, New Orleans, LA 70112-2234, USA.
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Imamura SI, Adams JC. Changes in cytochemistry of sensory and nonsensory cells in gentamicin-treated cochleas. J Assoc Res Otolaryngol 2003; 4:196-218. [PMID: 12943373 PMCID: PMC3202711 DOI: 10.1007/s10162-002-2037-7] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Effects of a single local dose of gentamicin upon sensory and nonsensory cells throughout the cochlea were assessed by changes in immunostaining patterns for a broad array of functionally important proteins. Cytochemical changes in hair cells, spiral ganglion cells, and cells of the stria vascularis, spiral ligament, and spiral limbus were found beginning 4 days post administration. The extent of changes in immunostaining varied with survival time and with cell type and was not always commensurate with the degree to which individual cell types accumulated gentamicin. Outer hair cells, types I and II fibrocytes of the spiral ligament, and fibrocytes in the spiral limbus showed marked decreases in immunostaining for a number of constituents. In contrast, inner hair cells, type III fibrocytes and root cells of the spiral ligament, cells of the stria vascularis, and interdental cells in the spiral limbus showed less dramatic decreases, and in some cases they showed increases in immunostaining. Results indicate that, in addition to damaging sensory cells, local application of gentamicin results in widespread and disparate disruptions of a variety of cochlear cell types. Only in the case of ganglion cells was it apparent that the changes in nonsensory cells were secondary to loss or damage of hair cells. These results indicate that malfunction of the ear following gentamicin treatment is widespread and far more complex than simple loss of sensory elements. The results have implications for efforts directed toward detecting, preventing, and treating toxic effects of aminoglycosides upon the inner ear.
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Affiliation(s)
- Shun-ichi Imamura
- Department of Otolaryngology, Shinshu University School of Medicine, 3-1-1 Asahi, Matsumoto, Nagano 390-8621, Japan
| | - Joe C. Adams
- Department of Otology and Laryngology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, MA 02114, USA
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Takamaki A, Mori Y, Araki M, Mineharu A, Sohma Y, Tashiro J, Yoshida R, Takenaka H, Kubota T. Asphyxia and diuretic-induced changes in the Ca2+ concentration of endolymph. THE JAPANESE JOURNAL OF PHYSIOLOGY 2003; 53:35-44. [PMID: 12689356 DOI: 10.2170/jjphysiol.53.35] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Using Ca2+ -selective microelectrodes based on the neutral carrier, ETH-1001 with polyvinyl chloride (PVC), we have measured changes in the free Ca2+ concentration of guinea pig cochlear endolymph ([Ca](e)) after transient asphyxia or intravenous administration of diuretics. Under the control conditions, the endocochlear potential (EP) was +80 mV, and the [Ca](e) was in the range 1.4 x 10(-7)-2.4 x 10(-6) M (n = 16). Transient asphyxia (1-1.5 min) produced an increase in the [Ca](e) with a fall in the EP, whereas the cessation of the asphyxia led to a quick recovery of both [Ca](e) and EP to their control levels. Intravenous administration of furosemide (60 mg/kg) or bumetanide (30 mg/kg) also caused an increase in the [Ca](e) with a fall in the EP, followed by a gradual recovery of both [Ca](e) and EP. From these results, we obtained a significant correlation between EP and p[Ca](e) (= -log[Ca](e)), and conclude that (1) the [Ca](e) is extremely low, around 10(-6) M or less, under normal conditions and (2) the [Ca](e) is directly correlated with EP under physiological conditions.
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Affiliation(s)
- Atsuko Takamaki
- Department of Physiology II, Osaka Medical College, 2-7 Daigaku-machi, Takatsuki, 569-8686 Japan
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Hsu CJ, Tan CT, Shau WY, Chen YS, Yeh TH, Lin-Shiau SY. Na+,K+-ATPase and Ca2+-ATPase activities in the cochlear lateral wall following surgical induction of hydrops. Hear Res 2001; 156:95-103. [PMID: 11377885 DOI: 10.1016/s0378-5955(01)00270-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Na+,K+-ATPase and Ca2+-ATPase activities have not been studied quantitatively in the cochlea affected by endolymphatic hydrops. The present study was designed to measure quantitatively the Na+,K+-ATPase and Ca2+-ATPase activities in the cochlear lateral wall and the threshold of auditory brainstem response (ABR) for guinea pigs in the early stages (=2 months) of experimentally induced endolymphatic hydrops. A significant negative association was demonstrated between Ca2+-ATPase activity and the change in ABR threshold for hydropic cochleae (P=0.014), but not for control cochleae (P=0.123), although no such significant association was revealed between Na+,K+-ATPase activity and any change in ABR threshold for both hydropic cochleae (P=0.751) and control cochleae (P=0.352). A significant increase in Ca2+-ATPase activity in the cochlear lateral wall was observed for the hydropic ear, in which normal ABR thresholds were maintained, as compared to the control ear. On the contrary, a mild decrease in Ca2+-ATPase activity in the cochlear lateral wall was observed for the hydropic ear, in which ABR thresholds increased significantly. The present findings suggest that alterations of Ca2+-ATPase activity in the cochlear lateral wall may implicate disturbed calcium-homeostasis in the inner ear, resulting in hearing dysfunction in the early stages of experimentally induced endolymphatic hydrops.
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Affiliation(s)
- C J Hsu
- Department of Otorlaryngology, National Taiwan University Hospital, Taipei.
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Hsu CJ, Shau WY, Chen YS, Liu TC, Lin-Shiau SY. Activities of Na(+),K(+)-ATPase and Ca(2+)-ATPase in cochlear lateral wall after acoustic trauma. Hear Res 2000; 142:203-11. [PMID: 10748339 DOI: 10.1016/s0378-5955(00)00020-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Na(+),K(+)-ATPase and Ca(2+)-ATPase are well known participants in the active transport of ions in the inner ear. These two enzymes play an important role in maintaining cochlear function. Although changes in these enzymes' activities in the cochlea have been implicated in noise-induced hearing loss, no evidence of quantitative alteration of Na(+),K(+)-ATPase or Ca(2+)-ATPase activities has ever been shown. The present study was undertaken to determine the quantitative alterations of their activities by microcolorimetric assay in the cochlear lateral wall after acoustic trauma. Adult albino guinea pigs were exposed to white noise at 105+/-2 dB A for 10 min or 40 h. The age-matched control animals were not exposed to noise. Noise exposure resulted in a significant threshold shift of the auditory brainstem response (P<0.001). Significant decreases in activities of Na(+),K(+)-ATPase and Ca(2+)-ATPase were found in the cochlear lateral wall after noise exposure (P<0.001). Statistical analysis indicated that a good correlation held not only between the decline of these enzyme activities and noise-induced hearing loss, but also between the gradual partial recovery of these parameters during the first 10-day recovery period. The present findings suggest that metabolic damage and ionic disturbance may contribute, at least partially, to noise-induced hearing threshold shift.
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Affiliation(s)
- C J Hsu
- Department of Otolaryngology, College of Medicine, National Taiwan University, No. 7, Chung-Shan South Road, Taipei, Taiwan.
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Agrup C, Bagger-Sjöbäck D, Fryckstedt J. Presence of plasma membrane-bound Ca(2+)-ATPase in the secretory epithelia of the inner ear. Acta Otolaryngol 1999; 119:437-45. [PMID: 10445058 DOI: 10.1080/00016489950180964] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
The Ca2+ concentration of the endolymph is low, around 0.023 mM. Yet, because of the positive endocohlear potential, Ca2+ must be actively transported into the endolymphatic space. The mechanisms responsible for the active Ca2+ transport into the endolymph are not known. In this study, the presence of plasma membrane-bound Ca(2+)-ATPase (PMCA ATPase) in the endolymph-producing, secretory epithelia of the inner ear from guinea pig was investigated with immunoblotting and immunohistochemistry. The antibody used was a monoclonal antibody which recognizes an epitope shared by all four known isoforms of PMCA ATPase. With immunoblotting, a band corresponding to PMCA ATPase was found in the stria vascularis, the ampullary tissue, the utricle and the endolymphatic sac in assays from at least three different batches of tissue. With immunohistochemistry, a strong positive staining reaction for PMCA ATPase could be seen in the stria vascularis and the dark cells of the ampullary tissue and the utricle. The epithelial cells in the endolymphatic sac showed a moderate positive staining reaction. Accordingly, in this study the presence of PMCA ATPase was shown in all the endolymph-producing, secretory epithelia of the inner ear. These results indicate that PMCA ATPase plays a role in the regulation of the Ca2+ concentration in the endolymph.
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Affiliation(s)
- C Agrup
- Department of Otorhinolaryngology, Karolinska Institutet, Karolinska Hospital, Stockholm, Sweden
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