噪声暴露对大鼠耳蜗碳酸酐酶活性及mRNA表达的影响

目的：探讨噪声暴露后耳蜗碳酸酐酶（CA）活性及其mRNA表达的变化。方法：选用健康白色大鼠24只，随机分为4组，1组为正常对照组，另外3组为实验组。实验组暴露在4kHz、110dBSPL窄带白噪声环境中4h／d，分别测试噪声暴露1d、1周、3周和对照组大鼠脑干反应（ABR）。采用免疫组织化学法观察耳蜗外侧壁CA的活性，RT-PCR检测大鼠耳蜗CAIImRNA的表达。结果：噪声暴露后大鼠ABR阈值较对照组显著增加；而耳CA活性及CAIImRNA的表达较对照组显著下降；随着噪声暴露时间的延长，ABR阈值增加而cA活性及CAIImRNA的表达呈下降趋势。结论：噪声刺激能降低耳蜗CA的活性及CAIImRNA的表达，CA可能参与了噪声性聋的发病机制。

The changes of carbonic anhydrase activity and its mRNA expression in rats cochlea after noise exposure

Objective：To investigate the changes of carbonic anhydrase（CA） activity and its mRNA expression in rats cochlea after noise exposure. Method：Twenty-four healthy Sprague Dawley rats were randomly allocated in- to 4 groups including 1 control group without contact of noise and 3 experimental groups exposed to a narrowband white noise of 4 kHz, 110 dB SPL 4h/d for t day, 1 week and 3 weeks, respectively. ABR thresholds were tested for each group at the time points described above. An immunohistochemical method was used to detect the expres- sion of CA in the cochlea tissue. Differences in CAII mRNA expressions with and without noise exposure were ex- amined using RT-PCR. Result：The thresholds of ABR in noise exposed cochlea were increased compared with the control cochlea（P〈0.01）. CA activity and the CAII mRNA expression in noise exposed cochlea were decreased compared with the control cochlea（P〈0.01） . The increase of ABR thresholds and decreases of CA activity and CAII mRNA expression showed a time dependent pattern as the extension of duration exposed to noise. Conclu- sion：Noise exposure could downregulate the CA activity and CAII mRNA expression in the cochlea. CA was prob- ably involved in the pathogenesis of noise-induced hearing loss.