Temporal changes in expression of aquaporin3, -4, -5 and -8 in rat brains after permanent focal cerebral ischemia

Morbidity and mortality in stroke are attributed to cerebral edema. To date, six aquaporins (AQPs) have been found in rat brains. Whereas studies have been focused on AQP1, -4 and -9, little is known about the expression of AQP3, -5 and -8. To clarify roles of AQP3, -5 and -8 in water movement, we examined the expression patterns of AQP3, -5 and -8 in ischemic brains from the rats with permanent middle cerebral artery occlusion (pMCAO). We also investigated the expression of AQP4 after ischemia, which was used as a positive control. We found that the expression of AQP4 increased continuously until 24 h after pMCAO in both the ischemic core and the border region. The increased expression was correlated with brain swelling, whereas the expression of AQP3, -5 and -8 continued to increase until 24 h after pMCAO in the border region but decreased 6 h after pMCAO in the ischemic core. We also found AQPs were colocalized with GFAP-positive astrocytes and/or NeuN-positive neurons in rat brains. This is the first study describing the expression of AQP3, -5 and -8 in rat brains subjected to pMCAO. Our findings indicated that dynamic changes of AQP3, -4, -5 and -8 expression could contribute to the development of cerebral edema after brain ischemia. Besides, AQP3, -5 and -8 may be involved in the neuronal swelling.