α-lipoic Acid Protection For Gentamicin-induced Wistar Rat Cochleotoxicity

IntroductionROS ( reactive oxygen species) plays an essential role in the inner hair cell' s death caused by AmAn. Gentamicin can activiate more NMDA and product amount of NO, NO₂^-, NO₃^-. They can damage the cochlea and tthereby cause hearing loss. Some scholars considered antioxidant material can protect or decrease the cochleotoxicity. We choose GM to construct a model of ototoxicity with emphasis on AmAn and use the higher effective antioxidant a - lipoic acid to protect organ of corti of cell from the damage. The finding reported here a — lipoic acid can effectively reduce GM - induced cochleotoxicity.Material and methodsMaterial: 25 healthy Wistar rat of either sex with body mass of 350g -400g,with sensitive preyer's reflexes. The animal wererandomly divided into three groups. Control group ( n = 5 ) , GM group ( n = 10) , GM + LA group ( n = 10). GM group, received gentamicin sulfate 100 mg/kg daily by intraperitoneal injections; GM + LA group,received gentamicin sulfate 100 mg/kg and injectioα -lipoic acid 10 mg/kg daily by intraperitoneal injections simultaneously; Control group, received the equivalent of sterile saline by intraperitoneal injections. Duration of treatment was 10 days for all groups. Body mass was montiored daily, and the administered dose was adjusted accordingly.DPOAE measurements were performed for each group before drug administration , 11 days after the start of drug treatment. The procedure was performed in a sowndproof shielded room as described previously.Preparation of cochlear specimens: After the last DPOAE measurement, ratwere decapitated immediately,and the temporal bones were removed guickly. The round and oval windows and the apex of the chochlea were opened, perfused with 4% paraformal - dehyde,and fixed 3h. After removal of the bony capsule basilar membrane and stria rascularis were isolated and filters for HE. The data were analyzed by Students Test.ResultsAfter 10 days of drug injection,The amplitudes of DPOAE at any frequency declined remarkably in GM group. ( p < 0. 01 ) Although the amplitudes of DPOAE in GM + LA were also signiflciantly declined after drug treatment, but they were lower than those in GM group. ( p <0.05 ) Great damage in both inner hair cell and out hair cell were observed in GM group. The damage in outer hair cell and undamaged in inner hair cell were observed in GM + LA group. There was no significant difference in control group.DiscussionGM - induced cochleotoxicity, is reported that it can product more NO and ROS. Those can damage the cochloa and hearing loss. We found the amplitudes of DPOAE declined remarkably in GM group and both inner hair cell and outer cell were damaged. While those decline and damagement were not significantly observed in GM + LA group. So a - LA,can prevent the damage of GM to hair cells. It maybe a very promissing medicine to the inner ear disorder. As a higher effective and safety antioxidant, a - LA can removed variety ROS in the body.Conclusiona - lipoic acid, a higher effective antioxidant material can effectivelly protect GM - induced cochleotoxicity.