[Role of ion channel Na-K-2Cl and alpha2 Na, K-ATPase in cochlear potassium cycling and auditory function].

Objective: To investigate the auditory function and the role of NKCC1 and alpha2 Na, K-ATPase in the potassium recycling of cochlea.

Methods: NKCC1(+/-) / alpha2 Na, K-ATPase(+/-) mice model was established from NKCC1(+/-) and alpha2 Na, K-ATPase(+/-) mice. The auditory function of all strain mice were detected by auditory brainstem response (ABR) and endocochlear potential (EP) to investigate the role of NKCC1 and alpha2 Na, K-ATPase in the potassium recycling of cochlea. Furosemide and ouabain were applied to block the two channels in Castel mice line which can long-time maintain normal auditory function and then their auditory function was detected by ABR to authenticate the mode of potassium recycling in vivo and the relationship between cochlear potassium recycling and NKCC1(+/-) and alpha2 Na, K-ATPase.

Results: The mean value for ABR thresholds in response to stimulus was elevated in NKCC1(+/-) and alpha2 Na, K-ATPase (+/-) mice [(38.49 +/- 12.29) dB and (53.32 +/- 7.62) dB) ] respectively, which was significantly increased compared with that observed in wild type mice [(23.13 +/- 3.78) dB, P < 0.05) ]; The EP value of NKCC1(+/-) [(78 +/- 7) mV] and alpha2 Na, K-ATPase(+/-) mice [(71 +/- 14) mV] was decreased compared with that of NKCC1(+/-) / alpha2 Na, K-ATPase(+/-) mice [( 86 +/- 11) mV]. The auditory function of NKCC1(+/-) / alpha2 Na, K-ATPase(+/-) mice could simulate the model of cochlear potassium recycling well. NKCC1 and Na, K-ATPase were great of importance in the potassium recycling, while the two ion channels were in restrict dynamic equilibrium. Castel mice line after administration with furosemide developed significant ABR threshold shifts (P < 0.05) compared with control group. Castel mice line after administration with ouabain also developed greatly significant ABR threshold shifts (P < 0.05) compared with control group. ABR threshold shifts in mice after administration both furosemide and ouabain was attenuated compared with only administration with furosemide (P < 0.01).

Conclusions: Ion channel NKCC1 and alpha2 Na, K-ATPase played important roles in the inner ear potassium recycling. Dysfunction of either of them could influence potassium concentration in the endolymph and lead to hearing loss subsequently. The role of NKCC1 and alpha2 Na, K-ATPase in cochlear potassium recycling was authenticated in vivo. The two ion channels contribute the key role for dynamic equilibrium in cochlear potassium recycling and are of great importance for the metabolism of potassium in the inner ear to maintain the normal auditory function.