兔神经源性尿路障碍输尿管功能变化及BKca表达研究

Study on the ureter function and expression of BKca in the ureter smooth muscle cell of rabbits with neuropathic urinary tract dysfunction

目的探讨兔神经源性尿路障碍（neurogenic urinary tract dysfunction，NUTD）输尿管功能改变及大电导钙激活钾通道（large-conductance Ca^2＋-activated K^＋ channels，BKca）的表达变化。方法将30只日本大耳白兔，体重2．0～2．5kg，编号后查随机数字表随机均分为NUTD组、实验对照组和空白对照组；其中NUTD组给予破坏L6以下脊髓，2周后行脊柱MRI和影像尿动力学检查证实存在明确神经损害，膀胱表现为逼尿肌无收缩但无膀胱输尿管反流；实验对照组仅咬除棘突，未破坏脊髓，2周后行脊柱MRI和尿动力学检查证实不存在明确神经损害，无明显膀胱尿道功能障碍。模型建立后2个月，3组家兔均进行影像尿动力学测定、输尿管功能和形态学观察，并应用免疫组织化学法、荧光定量PCR和Western-blot检测其输尿管平滑肌细胞（USMC）BKca mRNA和蛋白表达情况。结果发现动物模型建立后2个月NUTD组表现为逼尿肌无收缩，无膀胱输尿管反流发生；在1ml·kg^-1·min^-1恒定速度静脉滴注生理盐水条件下，NUTD组30min内产生尿量为（18．5±3．7）ml，实验对照组为（19．5±2．4）ml，空白对照组为（17．8±3．2）ml，三组间差异无统计学意义。左侧输尿管蠕动次数NUTD组为（39．0±3．0）显著低于实验对照组（44．0±5．0）和空白对照组（46．0±4．0），差异有统计学意义（P〈0．05）；光镜下NUTD组输尿管各层无明显变化；NUTD组USMC中BKcaαmRNA（2．89±0．67）和BKcaβ mRNA（4．59±1．22）表达相对于空白对照组mRNA（BKcaα：1．02±0．21；BKcaβ：1．03±0．28）平均分别上调2．89和4．59倍，差异有统计学意义（P〈0．001）；NUTD组BKcaα（1．35±0．32）和BKcaβ（1．47±0．10）蛋白表达相对于空白对照组（BKcaα：0．89±0．10；BKcaβ：1．03±0．13）显著上调，差异有统计学意义（P〈0．001）。结论NUTD早期在未发生膀胱输尿管反流和输尿管光镜病理改变时即已发生输尿管功能障碍，输尿管平滑肌细胞BKca表达水平升高抑制输尿管USMC兴奋性和收缩性可能是其输尿管功能障碍的原因之一。

Objective To investigate the changes of ureter function in rabbits with neuropathic urinary tract dysfunction （NUTD） and the expression of large-conductance Ca^2＋-activated K^＋ channels （BKca） in ureter smooth muscle cell. Methods Thirty Japanese White Rabbits were randomly divided into NUTD group （n = 10）, experimental control group （n = 10） and blank control group （n = 10）. With a spinal cord transaction at the sixth lumbar level and the sacral cord destroyed, the NUTD group showed significant nerve damage, acontractile detrusor （ACD） without vesieoureteral reflux （VUR） in spine MRI examination and video-urodynamic assessment after two weeks. In experimental control group, only part of spinous process was bitten at the same position and spinal cord exposed without a transaction. In blank group, no operation was performed. Video- urodynamie assessment, the observation of ureter function and morphology were performed 2 months after operation. The mRNA and protein expressions of BKca in ureter smooth muscle cell （USMC） were measured by real-time fluorescent quantitative PCR, immunohistochemistry and Western blot. Results Aeontractile detrusor was found in all animals from NUTD group without vesieoureteral reflux. There was no significant difference in urine volume among the three groups [NUTD group： （18. 5 ± 3. 7）ml, experimental control group： （19. 5 ± 2. 4）ml, Blank control group： （17. 8 ± 3.2）ml]. However, the peristalsis frequency of left ureteral in NUTD group （39. 0 ± 3. 0） was significantly lower than that in experimental control group （44. 0 ± 5.0） and blank control group （46. 0 ± 4. 0, P〈0. 05）. There were no abnormal changes in ureteral lamina epithelialis, lamina propria and muscular layer under light microscope among NUTD group. Compared with blank control group （BKcaα mRNA： 1.02 ± 0. 21, BKcaβ mRNA： 1.03 ±0. 28; BKcaα protein： 0. 89 ± 0. 10;BKcaβ protein： 1.03 ± 0. 13）, the mRNA expressions of BKcaα （2. 89 ± 0. 67） and BKcaβ（4. 59 ± 1.22） were respectively up- regulated for 2. 89 and 4. 59 times in NUTD group （P〈0. 001）, and expressions of BKcaα （1.35 ± 0. 32） and BKcaβ （1.47 ± 0. 10） protein also significantly increased （P〈0. 001）. Conclusions The ureter dysfunction occurs prior to vesicoureteral reflux and the pathological changes in ureter of the rabbits with NUTD. The increased expression of BKca inhibits the ureteral excitability and contractility, which may play an important role in upper urinary tract dysfunction of the rabbits with NUTD.