EXPRESSION OF AQUAPORIN-4 DURING CYTOTOXIC EDEMA AFTER CEREBRAL ISCHEMIC REPERFUSION IN RATS

To investigate the rule of the Aquaporin-4 (AQP-4) expression in cytotoxic edema after Cerebral Ischemic Reperfusion (CIR). Methods CIR models were established by occluding unilateral Middle Cerebral Arteries (MCA) of rat with nylon filament. 48 SD rats were divided into 2 groups randomly, including false operation group A(n=12) and operation group B (blood flow blocked 1 hours and the reperfusion for 24h, n=24). Both groups were examined with DWI and T2WIMRI. The relative ADC (rADC), relative density(rd), and relative area (rs) of the biggest hyperintensity signal layer on DWI were measured. Then the animals were sacrificed and perfused with the mixture solution consisting of TTC at different time intervals. The AQP-4 expression was measured with the image analyzer. Meanwhile, histologic examination was performed at each group. Results In the operation group, abnormal high intensity was found in DWI of ipsilateral MCA territory at15 min after MCAO, and rADC value decreased quickly within1 h after MCAO, while the AQP-4 expression, the rd-DWI and the rs-DWI increased rapidly in the stage. With the progress of the time after reperfusion, the rADC value increased slowly till 24h, and the rs-DWI decreased rapidly in the stage. While the AQP-4 expression (Delta S) decreased rapidly in the penumbra but increased still in the center area. Conclusion The high expression of AQP-4 in the acute ischemic cerebral tissues played a significant role in the cytotoxic edema. Certainly, it was also one of the important reasons of the decrease of rADC and hyperintensity on DWI in the early stage of the cerebral ischemia.