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

上皮性钠通道(ENaC)在膀胱过度活动症发病机制中作用的研究背景：膀胱过度活动症(OAB)是国际大陆学会于2002年提出的以症状为基础的综合征，是一种以尿急为主要症状的储存功能障碍。引起尿急的机制尚未被揭示，尽管已经推测它与传入传递的异常有关。人们已经注意到无髓C纤维的重要作用，其中香草素受体(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，尿路上皮细胞产生包括三磷酸腺苷在内的递质，影响膀胱感觉的传递(Fry，C.H.：Uroology，2004)。因此，我们研究了…的一种上皮性钠通道材料与方法：1)人体研究：研究对象为无膀胱出口梗阻和伴有OAB症状的良性前列腺增生症患者的尿失禁。用抗ENaC亚单位多克隆抗体的免疫荧光染色检测ENaC蛋白的表达，用定量RT-PCR法检测ENaC基因的表达。2)体外实验：取无膀胱出口梗阻和部分尿路梗阻的雌性大鼠尿路标本。用抗ENaC亚单位多克隆抗体的免疫荧光染色检测ENaC蛋白的表达，用定量RT-PCR法检测ENaC基因的表达。3)在大鼠体内的研究：在膀胱测压时评估逼尿肌的收缩能力和排尿间期。结果：1)人体研究：在人的膀胱中检测到ENaC亚单位蛋白(α，β，γ)的表达。2)大鼠(体外)研究：在大鼠膀胱中检测到ENaC亚单位(α，β，γ)的蛋白表达，尽管在有和没有膀胱出口梗阻的膀胱中各亚单位的表达水平在数量上没有差异。3)ENaC抑制剂阿米洛利不改变逼尿肌的收缩能力，结论与讨论：人和大鼠膀胱组织中ENaC亚单位(α，β，γ)基因的表达水平存在明显的种属差异，提示ENaC可能参与了膀胱过度活动的诱导。较少

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