Express Of Nitric Oxide Synthase Isoforms In The Cochlear Of Guinea Pigs After Ischemia-reperfusion

【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 investigate the express of oxide synthase isoforms in the normal cochlear of guinea pigs3. To investigate the express of oxide synthase isoforms in the cochlear of guinea pigs after ischemia reperfusion in different time4. 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 drug treatedgroup given dexamethasone 2mg/kg 30minutes before onset of ischemia. Every groups have8 guinea pigs and we will take samples 30 minutes after ischemia,6 hours after reperfusionand 24 hours after reperfusion in the last two groups.The methods to establish the model of ischemia reperfusion in cochlear of guinea pigs:one side of common carotid artery was occluded by specialized microvascular clamp and twosides of vertebral arterys were scorched, then the clamp was removed and the blood flowrestored at the time point (6hour,24hour). The negative control group was just opened andexposed the arterys. The hismorphology of cochlear was observed with hemotoxylineosin(HE) staining. The NOS immunoactivity in cochlear was studied by immunohistochemistyand labeling ratio of NOS expression was studied by image analysis.【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 than thegroups in the same time points without drugs. There is slight positive expression of NOS isforms in the hair cell, the striavascularis ,the spiral ligament,the membrane spiralis ,the endothelial lining of cochlearglomeruli and the spiral ganglion. In the ischemia groups, labeling ratio of NOS isformsexpression decreased significantly compared with the normal group and the control group.But in the reperfusion groups, there is only the labeling ratio of iNOS expression decreasedsignificantly. Compared with the 24 hours reperfused groups, the labeling ratio of iNOSexpression in cochlear increased in drug groups, and at the same time, the labeling ratio ofeNOS expression in cochlear drcreased significantly.【Conclusion】We can establish the model of ischemia-reperfusion in cochleas of guinea pigsby specialized microvascular clamp and scorched two sides of vertebral arterys. Lesions weredetected in the hair cell and the stria vascularis in ischemia group and reperfusion groups,and it is better in the drug groups. There is slight positive expression of NOS isforms in thenormal cochlear. iNOS products high level of NO which lead to the cochlear injury in theischemia reperfusion, and it can inhibit the expression of eNOS which can product level ofNO to protect the cochlear. The therapy of dexamethasone preserve the cochlear in theischemia reperfusion injury by blocking the expression of iNOS.