Physiological function of plasma membrane Ca2+-ATPase isoform 2 in inner ear hair cells of mouse

AIM: To investigate the auditory and balanceable function of hair cell plasma membrane Ca²⁺-ATPase isoform 2 (PMCA2) channel in mouse inner ear.METHODS: Hearing threshold and endocochlear potential (EP) were measured in the PMCA2 homozygous mutants mice,heterozygous mice and wild-type mice by auditory brainstem response (ABR),distortion product otoacoustic emission (DPOAE) and EP recordings,respectively.RESULTS: The auditory function in PMCA2 wild-type mice was normal,the mean value for ABR thresholds in response to click sound stimulus was (13.75±11.08)dB SPL,EP was (91.3±11.0)mV.The mean value for ABR thresholds in response to click sound stimulus was (63.89±12.90)dB SPL in PMCA2 heterozygous mice and significantly increased relative to that observed in PMCA2 wild-type mice (P<0.01).EP in PMCA2 heterozygous mice was about (80.7±9.0) mV and lower than that in PMCA2 wild-type mice but no statistics significance was observed (P>0.05). DPOAE thresholds increased and reduced amplitudes at high frequencies in PMCA2 heterozygous mice compared to wild-type mice.PMCA2 homozygous mutant mice were completely deaf,the ABR wave form was not observed even 100 dB SPL sound stimuli was used,the value of EP was (56.6±13.0) mV lower than that in PMCA2 wild type mice (P<0.05).PMCA2 homozygous mutants mice did not produce DPOAEs,PMCA2 homozygous mutant mice were deaf and demonstrated difficulties in maintaining their balance.CONCLUSION: These data demonstrate that PMCA2 is required for both balance and hearing and suggest that it may be a major Ca²⁺ pump used in endolymph Ca²⁺ maintenance.