響音傷害對聽力及耳蝸碳酸脫水酵素活性之影響

Effects of Acoustic Trauma on Hearing and Activity of Carbonic Anhydrase in the Cochlea

響音傷害會造成聽力損失，可能的機轉包括響音對內耳構造的直接機械傷害、內耳的代謝障礙和循環障礙。本研究之目的乃探討響音傷害對聽力及內耳碳酸脫水酵素活性之影響。將腦幹聽力閾值正常之白色天竺鼠暴露於1000赫茲(hertz, Hz)純音105分貝(dB SPL)中48小時，於停止響音後立刻測兩耳之腦幹聽力閾值，並於2星期後再測兩耳腦幹聽力閾值。耳蝸取出後，經固定和脫鈣後，用振動切片機切取60um厚之切片，以Hasson氏溶液來顯示內耳碳酸脫水酵素活性，並比較響音暴露耳與控制耳間之差異。雖然響音暴露耳之腦幹聽閾平均值上昇，表示聽力有明顯損失，但只1耳有明顯的耳蝸形態變化和碳酸脫水酵素活性減弱，其餘響音暴露耳的耳蝸碳酸脫水酵素活性都未見明顯變化。耳蝸內碳酸脫水酵素活性與耳蝸聽覺功能的關係有待進一步研究。

The experimental animals were exposed to 1 kHz pure tone of 105 dB SPL for 48 hours in the free sound field. The sound-exposed animals were sacrificed 2 weeks or immediately after termination of sound exposure respectively. The ABR thresholds were measured before sound-exposure and re-measured just before decapitation. The control ears were not exposed to the sound. Auditory function was assessed according to the difference of ABR thresholds between pre-exposure and post-exposure to the sound. Vibratome sections of decalcified cochleas were made at a thickness of 60 um. Hasson's incubation medium was used to stain the activities of carbonic anhydrase. Although decreased auditory dysfunction was noted by the increase of the mean ABR thresholds of the sound-exposed ears, no recognized change of the enzymatic activity was shown in the stria vascularis and organ of Corti. The results of present study showed there was effect of acoustic trauma on the hearing, but not on the activity of carbonic anhydrase in the cochlea. It is indicated that further investigation concerning the possible role of carbonic anhydrase in the cochlear function is challenging.