兔实验性脊髓空洞前状态水通道蛋白4表达的变化

Expression of aquaporin 4 during development of experimential presyrinx state in rabbits

目的：探讨水通道蛋白4（aquaporin-4,AQP4）在实验性脊髓空洞前状态的表达变化。方法：56只新西兰白兔被随机分为高岭土（Kaolin）组（40只）、生理盐水组（8只）和假手术组（8只）。经枕大池注入Kaolin建立新西兰白兔脊髓空洞症模型,注入后1,3,7,14,21d用干湿重法测定脊髓含水量、用免疫组织化学、Western blot和RT-PCR技术检测脊髓空洞前状态脊髓含水量、AQP4及其mRNA表达变化。结果：Kaolin组动物于术后第3天脊髓含水量即有明显增加（68.35%±0.70%）,第7天达到高峰（72.92%±0.86%）,第21天稍有缓解（70.03%±0.77%）,但仍高于对照组;AQP-4于术后第3天开始减弱[积分光密度（integral optical density,IOD）320.5±44.2],第7-14天达到最低水平（IOD258.7±26.5）,到21天时回升（IOD321.5±46.1）,但仍低于对照组;而AQP4mRNA表达变化趋势与其蛋白含量变化相一致。线性回归分析发现,AQP4及其mRNA表达变化与脊髓含水量之间存在负相关（r=-0.769,P〈0.01;r=-0.955,P〈0.01）。结论：脊髓空洞前状态中出现了AQP4及其mRNA表达减少,可能参与了缺血、缺氧性脊髓水肿的形成。

Objective： To investigate the expression of AQP4 during the development of presyrinx state of experimental syringomyelia in rabbits. Methods： The experimental syringomyelia models of rabbits were established by intra-cisternal injection of Kaolin. The expression of AQP4, AQP4mRNA and the water content of upper cervical spinal cord were measured with immunohistochemistry, Western blot, RTPCR and dry-wet measurement on days 1,3,7,14, and 21 after operation, respectively. Results： Compared with animals of control group, the water content increased in those of Kaolin group from the 1 s, day （68.35% ±0.70% ）, reached its peak on the 7^th day （ 72.92% ± 0.86% ）, lasted to the 14^th day （72.58% ±0.55% ）, and then began to drop on the 21^st day（70.03%±0.77% ）, while AQP-4 immunoreactive expression decreased on the 3^st day [ integral optical density（IOD） 320.5 ±44.2 ], reached its minimum on the 7^th day（ IOD 258.7±26.5）, lasted to the 14^th day, and recovered partially on the 21^th day approximately（ IOD 321.5 ± 46.1 ）. RT-PCR found the decreasing of AQP4 mRNA coincided well with that of AQP4 immunoreactive expression in presyrinx state. The linear regression analysis indicated that expression of AQP4 and its mRNA in cervical cord had a negtive correlation with the change of spinal water content（r = -0. 769, P 〈 0.01 ;r = -0. 955, P 〈 0.01 ）. Conclusion： Downregulation of AQP4 and its mRNA expression may involve in edema formation in the presyrinx state of rabbits.