Gobet Rita, Norregaard Rikke, Cisek Lars J, Peters Craig A, Nielsen Søren, Frøkiaer Jorgen
Division of Urology, University Children's Hospital, Zurich, Switzerland.
J Urol. 2008 Jun;179(6):2396-401; discussion 2401-2. doi: 10.1016/j.juro.2008.01.160. Epub 2008 Apr 23.
Impaired concentrating capacity has been demonstrated in human refluxing kidneys and in kidneys of growing animals with experimental congenital vesicoureteral reflux. Aquaporin water channel proteins are the principal mediators of water homeostasis in the kidney. We examined the impact of experimental congenital vesicoureteral reflux on renal aquaporin protein expression.
Vesicoureteral reflux was surgically induced bilaterally in male fetal sheep at 95 days of gestation (term 140 days). Following birth animals received antibiotic prophylaxis, and reflux grades were assessed by fluoroscopic voiding cystogram. After sacrifice at age 6 months 1 kidney of each animal (5 refluxing kidneys, and 3 from normal age and sex matched controls) was retrieved, frozen in liquid nitrogen and used for immunoblotting. The second kidney was perfusion fixed and processed for immunohistochemical analysis.
Semiquantitative immunoblotting of inner medulla showed that vesicoureteral reflux was associated with a marked down-regulation in expression of aquaporin 1 (arbitrary units 7.0 +/- 4.3 vs 22.5 +/- 2.8, p <0.05) and aquaporin 2 (5.7 +/- 5.1 vs 24.8 +/- 3.8, p <0.05), which was confirmed by immunocytochemical analysis. Dot blot analysis revealed a homogeneous down-regulation of aquaporin 2 expression throughout the refluxing kidney to 0.029 vs 0.1 in normal kidneys (p = 0.026).
Progressively impaired renal concentrating capacity induced by experimental fetal reflux is associated with decreased levels of renal aquaporin 1 and 2 expression. This long-term down-regulation of aquaporin 1 and 2 provides important molecular evidence for a defect in resorptive capacity of water induced by vesicoureteral reflux.
在人类反流性肾脏以及患有实验性先天性膀胱输尿管反流的生长动物的肾脏中，均已证实其浓缩能力受损。水通道蛋白水通道蛋白是肾脏中水稳态的主要调节因子。我们研究了实验性先天性膀胱输尿管反流对肾脏水通道蛋白表达的影响。
在妊娠95天（足月为140天）的雄性胎羊中双侧手术诱导膀胱输尿管反流。出生后，动物接受抗生素预防，并通过荧光透视排尿膀胱造影评估反流分级。在6个月龄处死后，取出每只动物的1个肾脏（5个反流性肾脏，以及3个来自年龄和性别匹配的正常对照），在液氮中冷冻并用于免疫印迹。第二个肾脏进行灌注固定并用于免疫组织化学分析。
内髓质的半定量免疫印迹显示，膀胱输尿管反流与水通道蛋白1（任意单位7.0±4.3对22.5±2.8，p<0.05）和水通道蛋白2（5.7±5.1对24.8±3.8，p<0.05）表达的显著下调相关，免疫细胞化学分析证实了这一点。斑点印迹分析显示，整个反流性肾脏中水通道蛋白2表达均匀下调，与正常肾脏中的0.1相比为0.029（p = 0.026）。
实验性胎儿反流引起的肾脏浓缩能力逐渐受损与肾脏水通道蛋白1和2表达水平降低有关。水通道蛋白1和2的这种长期下调为膀胱输尿管反流引起的水重吸收能力缺陷提供了重要的分子证据。
