Expression Of Aquaporin-4 In Brain From Rats With Subarachnoid Hemorrhagic Edema

[Objective] Brain edema and serious neuron injury may take place in patients after they have experienced aneurismal SAH, induced by cerebral vasospasm and the increase of intracranial pressure, et al. However, people know little of the mechanism of brain edema. Aquaprions are special water permeability proteins which were founded extensively exist in the cell membrane of animals and plants in recent years. Among them, aquaprion 4 is widespread in brain, which concerns with the reabsorption of cerebrospinal fluid , brain edema and other metabolism of water. This study was taken to explore the relation of aquaproin 4 with brain edema after subarachnoid hemorrhage (SAH ), by observing the expression of aquaproin 4 in cerebral cortex ,thalamus on different times after rat received autologous blood injection into cisterna magna.[ Methods ] 62 adult Wistar rats were randomly divided into groups of normal, sham operation and SAH. 0.3ml autologous blood was obtained from the cut-off tail of rat and subarachnoid hemorrhage was induced by injection of autologous blood into the cisterna magna. In the sham operation group, 0.3ml saline instead of autologous blood was injected into the cisterna magna of rat, and in normal group the animals were normal rats. The SAH group and the sham operation group were divided to 7 groups by different postoperative time spot(lh, 8h,ld,2d,3d,5d and 7d after operation). The changes of brain water content (BWC) were measuered by the wet and dry weight methods. In situ hybridization was used to determine the expression changes of AQP4 protein in cerebral cortex ,thalamus on different times .[ Results ] In both normal group and sham operation group, only few cells with expression of AQP4 protein appeared, showing no significant difference(P>0.05). In SAH group, both BWC and AQP4 protein expression in rat cortex, thalamus and hippocampus were increased at 8 hours and reached peak at 2 days and went to the normal level at 7 days, 8h, 1d, 2d, 3d and 5d after SAH show significant at 0.05 level compared with normal and sham operation group (P<0.05 ) . The expression of AQP4 protein was positively correlated with BWC (r=0.9115~0.9332, p<0.01).[ Conclusion ] The expression of AQP4 protein was positively correlated with the brain edema after SAH. It suggests that AQP4 protein may play a important role in the pathophysiology of brain edema after SAH.