Disease relevance of Endolymph

• Whereas mutations in KCNQ1 cause deafness by affecting endolymph secretion, the mechanism leading to KCNQ4-related hearing loss is intrinsic to outer hair cells [1].
• When anoxia was induced in guinea pigs treated with kanamycin, the rate of decline of the electrochemical potential difference for K+ between the endolymph and perilymph was reduced when compared to normal guinea pigs [2].
• We hypothesized that perilymphatic perfusion of cholera toxin might increase endolymph volume by stimulating adenylate cyclase activity, providing us with a pharmacological model of acute endolymphatic hydrops (EH) [3].
• The endocochlear potential (first and third turns) was recorded, and the sodium, potassium, and chloride concentrations, and osmolality of the endolymph (first and third turns) and perilymph were determined at different intervals from 2 to 24 weeks after the induction of the hydrops [4].
• Streptomycin and similar drugs that may reduce the production of endolymph may eventually be the treatment of choice in Meniere's disease [5].

High impact information on Endolymph

• Taken together, our data indicate that KVLQT1 is responsible for both JLN and RW syndromes and has a key role not only in the ventricular repolarization but also in normal hearing, probably via the control of endolymph homeostasis [6].
• This suggests EphB2 may regulate ionic homeostasis and endolymph fluid production through macromolecular associations with membrane channels that transport chloride, bicarbonate, and water [7].
• Histological analysis of the inner ear structures of Kcnq1(-/-) mice revealed gross morphological anomalies because of the drastic reduction in the volume of endolymph [8].
• Cx43 must also play a critical role in the physiology of hearing, presumably by participating in the recycling of potassium to the cochlear endolymph [9].
• Shaker-with-syndactylism (sy) is a classic deaf mouse mutant and we show here that a second allele, sy(ns), is associated with abnormal production of endolymph, the fluid bathing sensory hair cells [10].

Chemical compound and disease context of Endolymph

• A correlation of the effects of normoxia, hyperoxia and anoxia on PO2 of endolymph and cochlear potentials [11].
• Temporary improvement in the hearing level and discrimination from the glycerin test in endolymphatic hydrops could be explained by this potential mechanism of endolymph volume reduction [12].
• During anoxia or after ethacrynic acid injection potassium concentrations in the cochlear endolymph and in the marginal strial cells decrease, while sodium concentrations increase [13].
• Streptomycin and similar drugs which may reduce endolymph production may eventually be the treatment of choice for Meniere's disease [14].
• Anoxia and local application of ouabain decreased the -Cl concentration and 36Cl uptake in the endolymph [15].

Biological context of Endolymph

• We conclude that the NSC channel is Ca(2+) activated, voltage-insensitive and involved in both constitutive K(+) and Na(+) reabsorption from endolymph while the BK channel might participate in the K(+) pathway under stimulated conditions that produce an elevated intracellular Ca(2+) or depolarized membrane potential [16].
• Furosemide injection is followed by a rapid, but reversible decrease of the endocochlear potential and eighth nerve action potential with a more gradual decrease of the endolymph potassium concentration [17].
• Results show that EA facilitates the entry of gentamicin into endolymph, while it does not affect the kinetics of the drug in perilymph [18].
• The role of G protein-mediated signal transduction in the production of endolymph, an extracellular fluid of unusual ionic composition, is beginning to be understood [19].
• Pharmacokinetics of furosemide in endolymph [20].

Anatomical context of Endolymph

• Gentamicin persistence in rat endolymph and perilymph after a two-day constant infusion [21].
• Nevertheless, expression of Twik-2 within the stria vascularis suggests a potential role for this protein as one of the terminal components of the potassium ion-recycling pathway that contributes toward its reabsorption into the endolymph [22].
• In the present study we have recorded luminal concentrations of K(+) and Na(+) from the ES and the endolymphatic sac potential (ESP) during cochlear endolymph volume changes [23].
• Effect of cisplatin administration on the electrochemical composition of endolymph in the rat cochlea [24].
• Otoconia processed in 0.1 M sodium cacodylate or HEPES buffered artificial endolymph (pH 7.4) showed normal morphology that was similar to controls [25].

Associations of Endolymph with chemical compounds

• However, when cells were exposed to high apically K(+)/low Na(+) fluid, mimicking endolymph exposure, I(sK)/KvLQT1 actually functioned as a strict apical to basolateral K(+) channel inhibited by clofilium [26].
• The positivity of a perchlorate discharge test and the malformations of membranous labyrinth fit well with the recent achievements on the role of pendrin in thyroid hormonogenesis and the maintenance of endolymph homeostasis [27].
• Na+-K+-activated ATPase in the ampullar dark cells may energize the ouabain sensitive ionic transports that are involved in the production of endolymph [28].
• Cochlear sensory transduction depends on active extrusion of sodium ion (Na(+)) from the luminal fluid, endolymph [29].
• HCO(3) (-) secreted from the ionocytes may serve as a barrier to neutralize H(+) diffused from the sensory macula while keeping the endolymph alkaline outside the sensory macula [30].

Gene context of Endolymph

• Strial marginal cells secrete K+ across the apical membrane into endolymph via the K+ channel KCNQ1/KCNE1, which concludes the cochlear cycle [31].
• In addition, Cdh23 is expressed in the urticulo-saccular foramen,the ductus reuniens, and Reissner's membrane, suggesting that Cdh23 may also be involved in maintaining the ionic composition of the endolymph [32].
• The effects of AVP on the endolymphatic sac (ES) of the inner ear, which is thought to mediate reabsorption of endolymph, were investigated [33].
• Endolymph volume in Slc26a4-/- mice was increased and tissue masses in areas normally occupied by type I and II fibrocytes were reduced [34].
• In non-neuronal cells, TREK-1 was immunodetected in the apical membrane of dark cells and transitional cells, both of which are involved in endolymph K(+) secretion and recycling [35].

Analytical, diagnostic and therapeutic context of Endolymph

• After intravenous injection of furosemide (25-100 mg/kg), the EP dropped precipitously and rapidly reached its minimum value, however, the chloride activity in endolymph decreased more gradually [36].
• Autoradiography data suggest that ES ribosome-rich cells are capable of synthesis and secretion of tyrosine-containing proteins and may thus be involved in regulation of the osmolarity of endolymph based on the capacity to bind cations as well as water molecules [37].
• In situ hybridization showed the expression of MR mRNA in marginal cells of the stria vascularis, suggesting that aldosterone may regulate microhomeostasis of the endolymph, presumably by modulating Na, K-ATPase activity [38].
• First, using immunocytochemistry, we demonstrated that PMCA2 is present in control mice inner and outer hair cell stereocilia where it could pump calcium into the endolymph and that PMCA2 is absent in dfw2J stereocilia [39].
• We have developed methods to accomplish this by injecting the volume marker ion hexafluoroarsenate (AsF6) into endolymph by iontophoresis [40].

References