谷氨酸兴奋毒性及牛磺酸干预对大鼠视网膜GFAP表达的影响

目的探讨谷氨酸兴奋毒性对大鼠视网膜神经胶质原纤维酸性蛋白(glial fibrillary acid protein, GFAP)的影响及牛磺酸干预对此的作用.方法于大鼠玻璃体内单眼一次注射40 nmol谷氨酸制备视网膜谷氨酸兴奋毒性模型,60只雄性SD大鼠随机分为6组:正常对照组,溶剂(玻璃体内注射PBS)对照组,谷氨酸组,牛磺酸干预高、低剂量组(分别于腹腔注射25 mg/kg及5 mg/kg牛磺酸),阳性对照组(腹腔注射0.5 mg/kg MK-801-NMDA受体特异拮抗剂).通过免疫组化、免疫印迹、RT-PCR检测玻璃体注射后24 h、3、7 d的大鼠视网膜谷氨酸、GFAP的蛋白及mRNA表达.结果玻璃体注射谷氨酸使视网膜内谷氨酸、GFAP的蛋白及mRNA表达量于注射后24 h迅速升高,注射后3、7 d逐渐下降.25 mg/kg牛磺酸可有效拮抗24 h时的视网膜谷氨酸、GFAP蛋白及mRNA升高,并使GFAP的蛋白及mRNA水平于注射后24 h、3、7 d逐渐上升.低剂量牛磺酸作用不明显.结论视网膜谷氨酸兴奋毒性使胶质细胞反应性一过性增强.一定剂量牛磺酸可降低视网膜谷氨酸含量,并使胶质细胞反应性逐渐上调,可能有助于削弱谷氨酸兴奋毒性.

Effects of glutamate excitotoxicity and taurine intervention on retinal expression of glial fibrillary acid protein in rats

Objective To study the effects of glutamate excitotoxicity and taurine intervention on retinal expression of glial fibrillary acid protein (GFAP) in rats. Methods The rat model of retinal glutamate excitotoxicity was established with an intravitreal injection of 40 nmol glutamate to one eye of the rats. 60 male adult Sprague-Dawlay rats were randomly divided into 6 groups: normal control group, vehicle control group (an intravitreal injection), glutamate treatment group, small dose taurine (5 mg/kg) intervention group, large dose taurine (25 mg/kg) intervention group and positive control group (an intraperitoneal injection of 0.5 mg/kg MK-801, a NMDA receptor antagonist). The glutamate content and expression of GFAP were determined with immunohistochemistry, Western blotting and RT-PCR respectively. Results Elevation of glutamate content, GFAP immunoreactivity (IR) and GFAP mRNA were found in 24 h after glutamate injection. Reduction of glutamate content, GFAP IR and GFAP mRNA occurred on day 3 and 7 after injection. Administration of 25 mg/kg of taurine partly abolished the elevation of glutamate content, GFAP IR and GFAP mRNA. Then GFAP IR and GFAP mRNA content returned to a gradual increase in a time-dependent manner. Injection of 5 mg/kg taurine failed to show any effect. Conclusion Glutamate temporarily excites glial activity. A certain amount of taurine such as 25 mg/kg can reduce the glutamate content in the retina and gradually improve the glial reactivity which is helpful to reduce excitotoxicity of glutamate.