The Ca2+ activity of cochlear endolymph of the guinea pig and the effect of inhibitors

Ikeda, Katsuhisa; Kusakari, Jun; Takasaka, Tomonori; Saito, Yoshitaka

doi:10.1016/0378-5955(87)90040-2

Cited by 78 publications

(46 citation statements)

References 28 publications

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“…In the mammalian cochlea, which has been most studied, the endolymphatic cation concentrations are: K¤, 160 mÒ; Na¤ < 1 mÒ; Mg¥, 10 ìÒ; Ca¥, 20-40 ìÒ (Bosher & Warren, 1978;Bosher, 1979;Ikeda et al 1987;Salt et al 1989). Similar values have been measured in the auditory organs of reptiles like the turtle (Johnstone, Schmidt & Johnstone, 1963;Crawford et al 1991).…”

Section: Ca¥ Permeation and Blocksupporting

confidence: 65%

“…In the cochlea, the free Ca¥ has been measured as •30 ìÒ in mammals (Bosher & Warren, 1978;Ikeda, Kusakari, Takasaka & Saito, 1987;Salt, Inamura, Thalmann & Vorba, 1989) and 65 ìÒ in turtles (Crawford et al 1991). The significance of the endolymph composition is unclear, and the low Ca¥ is especially puzzling if Ca¥ entry is a crucial step in controlling transducer adaptation.…”

mentioning

confidence: 99%

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Calcium permeation of the turtle hair cell mechanotransducer channel and its relation to the composition of endolymph

Ricci

Fettiplace

1998

The Journal of Physiology

152

124

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Recordings of mechanoelectrical transducer currents were combined with calcium imaging of hair bundles in turtle auditory hair cells located near the high‐frequency end of the cochlea. The external face of the hair bundles was perfused with a range of Ca2+ concentrations to study the quantitative relationship between Ca2+ influx and transducer adaptation. With Na+ as the monovalent ion, the peak amplitude of the transducer current decreased monotonically as the external [Ca2+] was raised from 25 μM to 20 mM. When Na+ was replaced with the impermeant Tris the transducer current increased with external [Ca2+]. These results indicate that Ca2+ can both permeate and block the transducer channels. The Ca2+ concentration for half‐block of the monovalent current was 1 mM. To quantify the Ca2+ influx, the fraction of transducer current carried by Ca2+ was measured using the change in bundle fluorescence in cells loaded with 1 mM Calcium Green‐1. The fluorescence change was calibrated by substituting an impermeable monovalent ion to render Ca2+ the sole charge carrier. In the presence of Na+, the fractional Ca2+ current was ≈10 % in 50 μM Ca2+, a concentration similar to that in endolymph, which bathes the hair bundles in vivo. The amount of Ca2+ entering was dependent on the identity of the monovalent ion, and was larger with K+, suggesting that the transducer channel is a multi‐ion pore. Over a range of ionic conditions, the rate of transducer adaptation was proportional to Ca2+ influx indicating that adaptation is driven by a rise in intracellular [Ca2+]. Shifts in the current‐displacement function along the displacement axis in different external Ca2+ concentrations were predictable from variation in the resting Ca2+ influx. We suggest that changes in the resting open probability of the transducer channels adjust the entry of Ca2+ to keep its concentration constant at an internal site. The results demonstrate that endolymph containing high K+, 50 μM Ca2+ and low Mg2+ concentrations, maximizes the transducer current while still allowing sufficient Ca2+ entry to drive adaptation. The hair cell mechanotransducer channel, in its permeation and block by Ca2+, shows behaviour similar to the voltage‐gated Ca2+ channel and the cyclic nucleotide‐gated channel.

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Section: Ca¥ Permeation and Blocksupporting

confidence: 65%

mentioning

confidence: 99%

Calcium permeation of the turtle hair cell mechanotransducer channel and its relation to the composition of endolymph

Ricci

Fettiplace

1998

The Journal of Physiology

152

124

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“…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] out into the interstrial space by PMCA-ATPase which resides on the basolateral membrane of marginal cells and on the membranes of fibrocytes. However, their hypothesis does not support the previous hypothesis that Ca 2ϩ is actively transported from the stria vascularis out into the endolymphatic space [1,2].…”

Section: ϫ7 -24ϫ10contrasting

confidence: 53%

“…(1) [Ca] e is maintained at an extremely low level of around 10 Ϫ6 M or less under normal conditions, and (2) the fall in EP induced by asphyxia or the administration of diuretics is always accompanied by a large increase in [Ca] -selective microelectrode [1]. Later, the [Ca] e was confirmed to be low (ϳ2ϫ10 Ϫ5 M), by several other studies that employed Ca 2ϩ -selective microelectrodes [2][3][4][5]. In the present study, however, we found that the [Ca] e under control conditions had a much lower value, about 10 Ϫ6 M, than those values reported by other investigators.…”

Section: Discussionmentioning

confidence: 65%

Asphyxia and Diuretic-Induced Changes in the Ca2+ Concentration of Endolymph.

Takamaki

Mori

Araki

et al. 2003

JJP

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“…5 Calcium metabolism in the inner ear is tightly regulated through calcium channels and Ca ++ -ATPase at concentrations that are low in the endolymph and high in the perilymph. 2,[6][7][8][9][10][11][12][13] In vivo detection of Ca ++ handling in the inner ear is valuable for both research and the clinical diagnosis of inner ear disease at an early stage. However, this technique is not yet available.…”

Section: Camentioning

confidence: 99%

Calcium Metabolism Profile in Rat Inner Ear Indicated by MRI After Tympanic Medial Wall Administration of Manganese Chloride

Zou

Pyykkö

2015

Ann Otol Rhinol Laryngol

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Objectives: To evaluate the efficacy of the novel method for the targeted delivery of Mn ++ to the inner ear and monitor calcium metabolism activity in the inner ear. Materials and Methods: Dynamic signal changes of Mn ++ in the rat inner ear were followed using T 1 -weighted magnetic resonance imaging (MRI) after administration of 2.5 µl MnCl 2 (500 mM) to the medial wall of the middle ear cavity. Results: Mn ++ passed through both the oval and round windows and distributed in the perilymphatic compartments, where it formed bright sharp lines along the fluid-cellular borders 12 minutes post administration and entered the endolymph sufficiently after 45 minutes. After 6 hours, the distribution of Mn ++ shifted from a fluid-dominant pattern to a cell-dominant pattern. Mn ++ concentrated in the area of the basilar membrane, periphery process, and soma of the spiral ganglion on day 2; became more distinguishable on day 4; declined on day 8; and remained detectable for 16 days post administration. Conclusions:The novel targeted delivery method efficiently introduced Mn ++ into the inner ear. The dynamic distribution pattern of Mn ++ in the inner ear shown by MRI indicates that this method can be used to monitor calcium metabolism activity in the inner ear.

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The Ca2+ activity of cochlear endolymph of the guinea pig and the effect of inhibitors

Cited by 78 publications

References 28 publications

Calcium permeation of the turtle hair cell mechanotransducer channel and its relation to the composition of endolymph

Calcium permeation of the turtle hair cell mechanotransducer channel and its relation to the composition of endolymph

Asphyxia and Diuretic-Induced Changes in the Ca2+ Concentration of Endolymph.

Calcium Metabolism Profile in Rat Inner Ear Indicated by MRI After Tympanic Medial Wall Administration of Manganese Chloride

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