噪声对豚鼠内耳组织能量代谢的影响——噪声致聋机理

THE EFFECT OF NOISE ON ENERGY METABOLISM IN THE INNER EAR TISSUES OF GUINEA PIGS——THE EMCHANISM OF NOISE-INDUCED HEARING LOSS

豚鼠暴露于125dB SPL噪声下1小时后即刻、1天内耳组织中葡萄糖(46.0±18.3μg/mg蛋白,102.2±56.3μg/mg蛋白)及丙酮酸量(30.6±8.4μg/g蛋白,47.1±15.7μg/g蛋白)均显著地高于对照组(葡萄糖26.4±8.9μg/mg蛋白,丙酮酸23.7±8.9μg/g蛋白),p<0.05。与此同时豚鼠听功能耳廓反射阈衰减dB值(30.0±12.2dB,44.8±2.5dB)显著地低于暴露前水平(49.4±2.9dB,46.2±1.9dB),P<O.05。噪声暴露后3天及7天内耳组织中葡萄糖、丙酮酸含量与对照组相比无显著差别的同时豚鼠听功能已恢复接近于暴露前水平。噪声暴露后内耳组织中ATP水平及能荷值与对照组相比无明显改变。豚鼠暴露噪声强度131dB SPL下1小时即刻,直至7天听功能均显著地异常,而内耳组织中葡萄糖、丙酮酸量仅在暴露后即刻及3天显著地高于对照组。我们认为在声强125dB下豚鼠听功能异常主要原因是噪声刺激加速内耳能量代谢但产生的代谢能ATP的总量仍不能满足维持正常功能所需。声强131 dB下听功能异常则主要由机械性损伤毛细胞所致。

Two hundred and seventy guinea pigs were used. Thirty guinea pigs were served as the control. The others received the noise exposure. Immediately and 1 day after noise exposure at the intensity of 125 dB SPL with time of 1 hour, the content of glucose (46.0±18.3 μg/mg protein, 102.2±56.3 μg/mg protein) and pyruvate (30.6±8.4 μg/mg protein, 47.1 ± 15.7 μg/mg protein) in the inner ear tissues of guinea pigs were significantly higher than that of the control (glucose 26.4 ± 8.9 μg/mg protein, pyruvate 23.7 ± 8.9 μg/g protein), p <0.05, but were not 3 days and 7 days after noise exposure. In the same condition, ATP level and energy charge in the inner ear tissues were not significantly differed from the control. The hearing reflex threshold attenuation dB in the left ear of guinea pigs immediately and 1 day after noise exposure (30.0±12.2dB, 44.8 ± 2.5dB) were significantly lower than the corresponding values before exposure (49.4±2.9dB, 46.2±1.9dB), P<0.05, but were not 3 days and 7 days after exposure. Based on the increasing content of glucose and pyruvate simultaneously with the steady ATP level and energy charge in the inner ear tissues accompanied by the decrease of hearing reflex threshold attenuation dB in guinea pigs, we conclude that the noise stimulation increased the energy demand and accelerated the energy metabolism rate in the inner ear tissues, and that the total amount of ATP generated by energy metaboilism was not enough to maintain the normal function of hearing, which was the main reason of noise-induced hearing loss under the intensity of 125 dB with time of 1 hour. Immediately to 7 days after noise exposure at intensity of 131 dB SPL wi th time of 1 hour, the hearing reflex threshold attenuation dB in the guinea pigs significantly decreased, P<0.05. The glucose and pyruvate content in the inner ear tissues significantly increased immediately and 3 days after noise exposure, P<0.05. In this condition, the auditory functional alteration was mainly caused by the mechanical damage.