Measurements of ionic concentrations along with endocochlear potential in wild-type and claudin 14 knockout mice

• Published in: Auris, nasus, larynx nasus, larynx, 2018-06, Vol.45 (3), p.421-426
• Main Authors: Shiraiwa, Yuka, Daikoku, Eriko, Saito, Masahisa, Yamashita, Yui, Abe, Takaya, Ono, Fumihito, Kubota, Takahiro
• Format: Article
• Language: English
• Subjects: Animals; Calcium - analysis; Claudin-14; Claudins - genetics; Cochlea - physiopathology; Endocochlear potential; Endolymph - chemistry; Evoked Potentials, Auditory, Brain Stem - physiology; Hair Cells, Auditory; Hydrogen-Ion Concentration; Ion concentrations in endolymph; Ion-selective microelectrodes; KO mouse; Membrane Potentials - physiology; Mice; Mice, Knockout; Potassium - analysis; Sodium - analysis
• ISSN: 0385-8146; 1879-1476
• DOI: 10.1016/j.anl.2017.07.013

To examine whether the changes in endolymphatic ion concentrations were involved in hair cells degeneration in claudin-14 knockout (KO) mice (Cldn14−/−), we measured the endocochlear potential (EP) along with concentrations of K+, Na+, H+, or Ca2+ ([K]e, [Na]e, pHe, [Ca]e) in Cldn14−/−, in which hair cells were selectively damaged, and compared with measurements in wild type mice (Wt). We used the Cldn14−/− from 3 weeks of age, in which the auditory brain responses (ABR) was severely diminished. Using double-barreled ion-selective microelectrodes, we measured [K]e, [Na]e, pHe, and [Ca]e in both Wt and Cldn14−/− at 8–10 weeks of age. (1) In Wt, the EP was +92mV. [K]e, [Na]e, pHe, and [Ca]e were 169mM, ∼1.0mM, 7.50, and 395nM, respectively. In the Cldn14−/−, the EP was +96mV. [K]e, [Na]e, pHe, and [Ca]e were 167mM, ∼1.0mM, 7.73, and 179nM, respectively. No significant differences in the above values were observed between Wt and Cldn14−/−. (2) A significant linear correlation between EP and [Ca]e (R=0.93) was observed for both Wt and Cldn14−/−, but no correlation was observed between EP and K+, Na+, or H+. These findings suggest that (1) the changes in endolymphatic ion concentrations might not be involved in hair cells degeneration in Cldn14−/−, (2) [Ca]e might be regulated by EP in both Wt and Cldn14−/−.