Abstract：OBJECTIVE: Aquaporin- 4 (AQP4) is a member of a family of water-selective channel proteins that is highly expressed in the brain. This study investigated the alterations of AQP4 expression and its relationship with cerebral edema monitored by magnetic resonance(MR) imaging in neonatal rats following hypoxia-ischemia (HI). METHODS: Seven-day-old neonatal rats were subjected to right carotid artery occlusion plus hypoxia in 8% oxygen. T2 values and apparent diffuse coeffcient (ADC) were acquired by MR imaging before HI, and 0, 1 and 24 hrs after HI. AQP4 expression in the brain and permeability of blood brain barrier were examined by immunohistological staining. Semiquantitive analysis of AQP4 protein was done by Western blotting. RESULTS: ADC significantly decreased in almost entire cerebral hemisphere ipsilateral to the occlusion at 0 hr after HI, recovered partially at 1 hr after HI, and at 24 hrs after HI the changes remained similar to that at 1 hr after HI. T2 values increased in the ipsilateral hemisphere at 0 hr after HI, recovered partially at 1 hr after HI, and then remained unchanged until 24 hrs after HI. IgG extravasation was observed at o hr after HI, and gradually increased after HI. AQP4 immunoreactive expression in the ipsilateral hemisphere to the occlusion decreased at 0 hr, 1 hr or 24 hrs after HI. The areas of AQP4 immunoreactive expression decrease coincided well with the regions of ADC and T2 changes after HI. Western blotting analysis demonstrated that AQP4 protein was not significantly reduced until 24 hrs after HI. CONCLUSIONS: AQP4 expression in the brain decreased in the neonatal rats following HI and the decrease of AQP4 expression may be involved in the development of acute HI cerebral edema. The rapid decrease in AQP4 immunoreactive expression following HI is likely due to conformational changes or translocation of AQP4 protein.
MENG Shu-Zhen,XIN Ying,HAN Xiao-Hua et al. Relationship between the decrease in aquaporin-4 expression and hypoxic-ischemic cerebral edema in neonatal rats[J]. CJCP, 2005, 7(4): 349-353.
