Expression Of Aquaporin1, 4 In The Cochlea Of Aged Rat

ObjectiveToday, the number of prebyscusis is growing increasingly. To the older people, it has great impaction on the quality of life. But so far the pathogenesis of presbycusis is not entirely clear. Aquaporins(AQP)are water channel with important roles in water flux across cell membranes. It has been confimed that there has seseveral hypotype of AQP in the inner ear of the mammalian. The volume of the endolymph and the homeostasis of the interal environment are crucial for the maintenance of the hearing and equilibrium function. It is theorized that AQP are important to the hearing. In current test, we detected the expression of AQP1, AQP4 in the cochlea of aged rat, to investigate the possible pathogenesis of presbycusis. So we can provide a theoretical basis for clinical prevention and treatment of prebyscusis.Materials and MethodsTo divided 30 healthy adult Wistar rats into two groups randomly: experimental group and a control group. Each group has 15 rats. To obtain the body weight of every rat, then experimental group was treated with intraperitoneal injection of D-galactose (300mg/kg) for four weeks in twice daily. The control group was received the same amount of intraperitoneal injection of saline for the same period. Every rat was examined the anditory brain response (ABR) thresholds, before and after treatment separately. When finished the treatment, rats were anesthetized with 10% chloral hydrate (0.1ml/kg) through intraperitoneal injection. Then open the chest, and use the normal saline to wash the blood through the left ventricle rapidly, then 4% paraformaldehyde phosphate buffer was used to perfuse slowly. After this, to decapitate quickly and to dislodge acoustic capsule immediately. As seen under the microscope, to remove the supernumerary bone arounding the cochlea. Those which were found to has otitis media were abandoned. Then place the sample into the 10%EDTA for ten days until we can clip the bone.completely. Finally the cochlea was embeded by paraffin and was sliced for the immunohistochemistry. Finally we use computer to exam IOD and statistical analysis was performd with SSPS10.0 software.ResultsCompare to the control group,in the experimental group, the thresholds of ABR elevated ,the latencies of waveâ… ,â…¡,â…¢delayed significantly. The expression of AQP4 was mainly located in the spiral ganglion cells and in the Hensen cells and Claudius cells of the Cortis.The expression of AQP1 was mainly located in the stria vascularis.Through Image Analysis System, we found IOD values of immunohistochemistry result of AQP4 in the experimental group were lower than that in the control group, and the difference was ststistically significant(p<0.05). But the IOD values of AQP1 don't have ststistically significant difference between the two groups.Conclusion AQP1,4 have definite distribution in the cochlea of aged rat. The expression of AQP4 was mainly located in the spiral ganglion cells and in the Hensen cells and Claudius cells of the Cortis, while the expression of AQP1 was mainly located in the stria vascularis. In the cochlea of aged rat, the AQP4 has a tendency of down regulation while AQP1 has no marked change. The regulation of AQP may alter the the homeostasis of the interal environment, which resulted the impairment of hearing.