The Observation of Cochlea Hair Cell Death and Expression of Caspase-3 after Intense Low Frequency Noise Exposure in Bama Pig / 听力学及言语疾病杂志

ABSTRACT

Objective To investigate the effects of intense low frequency noise on expression of caspase -3 in bama pigs ,and observe the death of cochlea hair cell .Methods 8 bama pigs were randomly divided into a normal control group(2 pigs) and experimental groups(6 pigs) .Auditory brainstem responses(ABR) were tested before the experiment .The control group was the same as the experimental groups except noise exposure .The experimental group was randomly divided into immediate group ,36 h group ,and 84 h group(2 pigs per group) .They were ex-posed to intense low frequency noise at 142 dB of 50 Hz for 5 min according to the three time points .ABR were test-ed again before the cochlea were collected at different time points .The expression of caspase -3 was studied through immunohistochemistry and immunofluorescence ,hair cell loss rate by counting to determine cell death .Results The average ABR threshold of 8 bama pigs(16 ears) before the exposure was 61 .25 ± 10 .72 dB nHL .ABR thresh-olds were not elicited after exposure to the noise .Different parts of bama pigs showed positive expression of caspase -3 in two ways .As time prolonged after exposure ,the positive expression of caspase -3 gradually weakened .The im-mediate group and 36 h group ,compared with the control group ,showed the apparent misplace of three out hair cells in the arrangement and levels .The 84 h group through immunofluorescence lost out hair cells ,and only inner hair cells were visible .Conclusion ABR thresholds were elevated after noise exposure .The procedure of hair cell nucleus damage and caspase-3 expression is different ,and the noise can induce opening apoptotic program of spiral ganglion .