Expression Of Inducible Nitric Oxide Synthase And Cell Apoptosis In Cochlear Of Guinea Pigs After Ischemia-reperfusion Injury

【Objective】To establish the animal model of ischemia reperfusion injury in cochlea of guinea pigs.1. To observe the change of morphology in cochlear after ischemia reperfusion in different time.2. To analysis the expression of iNOS in cochlear after ischemia-reperfusion in different time.3. To observe the cell apoptosis in cochlear after ischemia-reperfusion in different time.4. To analysis the relationship between the expression of iNOS and the cell apoptosis in cochlear after ischemia-reperfusion.5. To investigate the application of dexamethasone.【Methods】72 healthy guinea pigs were devided into the normal group, negative controlgroup, negative control group after the application of dexamethasone, model and drugtreated group given dexamethasone 2mg/kg 30minutes before onset of ischemia. Everygroups have 8 guinea pigs and we will take samples 30 minutes after ischemia,6 hoursafter reperfusion and 24 hours after reperfusion in the last two groups.The methods to establish the model of ischemia reperfusion in cochlear of guineapigs: one side of common carotid artery was occluded by specialized microvascular clampand two sides of vertebral arterys were scorched, then the clamp was removed and theblood flow restored at the time point (6hour,24hour). The negative control group was justopened and exposed the arterys. The hismorphology of cochlear was observed withhemotoxylineosin (HE) staining. The iNOS immunoactivity in cochlear was studied byimmunohistochemisty and labeling ratio of iNOS expression was studied by image analysis.The cell apoptosis was studied by TUNEL (terminal-deoxynucleotidy transferase mediatedd-UTP nick-end labeling). The analysis of variance were to compute the differencesbetween and among different experimental groups. Statistical significance was defined asP<0.05.【Result】There were no lesions of hair cells and stria vascularis in the normal control andthe sham oprated animals wherever the application of dexamethasone or not. Lesions weredetected in the hair cell and the stria vascularis in ischemia group. Compared with theischemia group, the lesions were more obvious in the reperfusion groups, especially inreperfusion 6hours groups. But the morphological changes of the Corti and the striavascularies in the groups that had been applicated dexamethasone were more subtle thanthe groups in the same time points without drugs. In the ischemia group and reperfusiongroups, labeling ratio of iNOS expression decreased significantly compared with thenormal group and the control group ( P<0.05). The labeling ratio of iNOS expression inevery reperfusion group decreased gradually compared with the ischemia group (P<0.05).Howevry, compared with the reperfused groups, the labeling ratio of iNOS expression incochlear increased in drug groups. There were almost no cell apoptosis in the normal groupand the control group. Compared with the two groups before, there were more cellapoptosis in the ischemia group and the reperfused groups (P<0.05). The numbers ofapotosis cells in the drug groups were smaller than the groups without drugs.【Conclusion】We can establish the model of ischemia-reperfusion in cochleas of guineapigs by specialized microvascular clamp and scorched two sides of vertebral arterys.Lesions were detected in the hair cell and the stria vascularis in ischemia group andreperfusion groups, and it is better in the drug groups. There is slight positive expression ofiNOS in the hair cell, the stria vascularis and the spiral ganglion. In the ischemia group andreperfusion groups, labeling ratio of iNOS expression decreased significantly comparedwith the normal group and the control group. Compared with the reperfused groups, thelabeling ratio of iNOS expression in cochlear increased in drug groups. There were almostno cell apoptosis in the normal group and the control group. But there were more cellapoptosis in the ischemia group and the reperfused groups (P<0.05). The numbers ofapotosis cells in the drug groups were smaller than the groups without drugs. All of aboveindicates that iNOS may get involve in the normal hearing conduct and it products highlevel of NO which lead to the cochlear injury in the ischemia reperfusion. Thevertebrobasilar ischemia reperfusion injury can cause the cell apoptosis in cochlear. Thetherapy of dexamethasone preserve the cochlear in the ischemia reperfusion injury byblocking the expression of iNOS. And this drug can inhibit the apoptosis caused byischemia reperfusion injury.