Elucidation on mechanisms of vanilloid and cannabinoid functions in the urogenital afferent neurotransmissions

上皮钠通道（epithelial sodium channel, ENaC）在膀胱过动症（overactive膀胱，OAB）诱发机制中的意义研究背景：膀胱过动症（overactive膀胱，OAB）是2002年国际尿失禁学会（International Continence Society）新定义的以症状为基础的综合征，是一种以尿急为基本症状的储尿功能障碍。引起尿急的机制尚未揭示，但据推测可能与传入传递异常有关。有人注意到无髓鞘c -纤维的重要作用，其中香草样受体（VR1, VRL1）在脊髓损伤等病理条件下大量表达，而传递尿感的机械感受器的本质尚不清楚。最近的研究表明，尿路上皮产生包括ATP在内的递质，影响膀胱感觉的传递（Fry， C.H.: Urology, 2004）。因此，我们研究了上皮钠通道（ENaC），这是参与膀胱机械感觉传导的更多候选通道之一。材料与方法：1)人体研究：取无膀胱出口梗阻且有OAB症状的良性前列腺增生患者的尿路上皮。采用抗ENaC亚基多克隆抗体免疫组织荧光染色检测ENaC蛋白表达，RT-PCR定量检测ENaC基因表达。2)大鼠体外实验：采用无膀胱出口梗阻和部分尿道梗阻的雌性大鼠尿路上皮。采用抗ENaC亚基多克隆抗体免疫组织荧光染色检测ENaC蛋白表达，RT-PCR定量检测ENaC基因表达。3)大鼠体内实验：膀胱术中测定逼尿肌收缩力和排尿间隔。还研究了ENaC抑制剂阿米洛利对这些参数的影响。结果：1)人的研究：在人膀胱中检测到ENaC亚基（α、β、γ）蛋白的表达。梗阻膀胱中各ENaC亚基mRNA的表达水平显著高于对照组（泌尿外科，64:1255-1260,2004）。2)大鼠体外实验：检测了ENaC亚基（α、β、γ）蛋白在大鼠膀胱中的表达，尽管各亚基mRNA的表达量在有和无膀胱出口阻塞的膀胱中没有定量差异。3)ENaC抑制剂阿米洛利不改变逼尿肌收缩力，但明显增加了排尿间隔时间。结论与讨论：本研究揭示了ENaC亚基（α, β, γ） mRNA的表达水平在尿道梗阻的人和大鼠膀胱中存在显著的物种差异，提示ENaC可能参与了膀胱过度活动的诱导。少

Backaround of the study on the significance of epithelial sodium channel (ENaC) in the mechanism inducing overactive bladder :Overactive bladder (OAB) is the symptom-based syndrome which was newly defined by the International Continence Society in 2002, and is a storage dysfunction exhibiting urinary urgency as an essential symptom. The mechanism inducing urinary urgency has not been revealed, although it has been speculated that it is involved in the abnormality in the afferent transmission. One has noted the significance on the role of unmyelinated C-fibers in which vanilloid receptors (VR1, VRL1) are largely expressed under pathologic conditions such as spinal cord injury, while the essence of mechanoceptors which convey urinary sensations is unknown. The recent studies demonstrated that the urothelium produced transmitters including ATP, influencing the transmission in the bladder sensory (Fry, C.H. : Urology, 2004). Thus, we examined the epithelial sodium channel (ENaC), one of th … More e candidates involved in the mechanosensory transduction in the bladder.Materials and Methods :1)Study in the human : Urothelia from patients without bladder outlet obstruction and with benign prostatic hyperplasia presenting OAB symptoms, were used. The expression of ENaC proteins was examined by immunohistofluorescent staining using anti-ENaC subunit polyclonal antibodies, and the ENaC genes expression was assessed by a quantitative RT-PCR.2)Study in the rat (in vitro) : Urothelia from female rats without bladder outlet obstruction and with partial urethral obstruction, were used. The expression of ENaC proteins was examined by immunohistofluorescent staining using anti-ENaC subunit polyclonal antibodies, and the ENaC genes expression was assessed by a quantitative RT-PCR.3)Study in the rat (in vivo) : Detrusor contractility and intermicturition interval were evaluated during cystometry. The effects of amiloride, an ENaC inhibitor, on these parameters were also examined.Results :1)Study in the human : The expression of proteins for ENaC subunits (α, β, γ) was detected in the human urinary bladder. The expression levels of each ENaC subunit mRNA in obstructed bladders were significantly greater than those in controls (Urology, 64 : 1255-1260, 2004).2)Study in the rat (in vitro) : The expression of proteins for ENaC subunits (α, β, γ) was detected in the rat urinary bladder, although the expression levels of each subunit mRNA were not quantitatively different between bladders with and without bladder outlet obstruction3)Amiloride, an ENaC inhibitor, did not change the detrusor contractility, whereas it markedly increased the intermicturition interval.Conclusions and Discussion :The studies revealed a remarkable species difference between the human and rat bladders with obstructed urethra in the expression levels of ENaC subunits (α, β, γ) mRNA, while these suggested the possibility that ENaC was involved in the induction of overactive bladder. Less