脑局灶性缺血再灌大鼠AQP4与Kir4.1表达与脑水肿正相关

Expression of AQP4 and Kir4.1 is positively related to brain edema after cerebral ischemia reperfusion

目的研究大鼠脑局灶性缺血再灌注(CIR)后水通道蛋白4(AQP4)与内向整流性钾通道(Kir4.1)在脑组织中的表达变化,探讨两者在脑水肿形成中的作用。方法 136只SD大鼠随机分为CIR组与假手术对照组,线栓法制作CIR模型,缺血2 h后再灌注。CIR后6、12、24、48和72 h以及7 d取出脑组织,干湿重法、伊文氏蓝(EB)测定法、免疫荧光双标和RT-PCR检测脑水含量(BWC)、血脑屏障(BBB)通透性、AQP4与Kir4.1mRNA的表达,计算两者表达量比值。结果 CIR后6 h开始,脑水含量呈时间依赖性增加,48～72 h达到高峰。EB含量在CIR后6 h开始增高,12/48 h出现双峰值。CIR后AQP4与Kir4.1在室管膜等水代谢密切相关界面上差异表达,各时间点AQP4与Kir4.1mRNA均较假手术组增高,CIR 12 h内两者比值较假手术组无明显差异,12 h后比值逐渐增大。结论再灌注早期脑水肿主要由血脑屏障开放引起,而AQP4与Kir4.1再分布在后期脑水肿的形成中发挥重要作用。

Objective To investigate the change of AQP4 and Kir4.1＇s expression to explore the mechanism of brain edema caused by CIR.Methods A total of 136 healthy SD rats were randomly divided into two groups,CIR group and control group.CIR models were established by occluding unilateral middle cerebral artery of the rats with suture method.The sutures were removed after two hours to allow reperfusion.The brain of the rats were taken out at 6 h,12 h,24h,48 h,72 h and 7 d after reperfusion.The change of brain water content（BWC） was measured by the wet and dry weight.AQP4 and Kir4.l were detected by immunofluorescence.The contents of AQP4 and Kir4.1 mRNA were detected by RT-PCR.Calculated the ratios of AQP4 mRNA and Kir4.1 mRNA.Results The BWC of ischemic brain tissue increased form CIR 6 h,and reached its peak during the CIR 48～72 h.The permeability of BBB increased after CIR,the increasing permeability had two peaks,at CIR 12 h and CIR 48 h respectively.AQP4 and Kir4.1 were co-expressed at cerebral pia mater,choroid plexes and ependyma.The expression of AQP4 and Kir4.1 mRNA increased after CIR.The ratio of AQP4 and Kir4.1 mRNA began to increased at 12 h after CIR.Conclusion In early stage after CIR,The increased capillary vessel per meability induced the brain edema;In the later stage.The redistributionof AQP4 and Kir4.1 played an important role in the pathological course of CIR brain edema.