The role of CGRP and eNOS in the pathophysiology of mixed urinary incontinence
Date Issued
2004
Date
2004
Author(s)
Yeh, Chung-Hsin
DOI
zh-TW
Abstract
背景
混合型尿失禁是指應力性尿失禁和急迫性尿失禁或逼尿肌不穩定合併存在的一種病況。長期以來有關治療的爭議一直是個重要的議題。有人認為應力性尿失禁是問題的根本所在，因為它讓尿液漏入近端尿道因而引發逼尿肌不穩定收縮或甚至急迫性尿失禁；就是所謂的尿道逼尿肌促進反射（urethrodetrusor facilitative reflex）的假説，因而主張先以手術的方法修正膀胱出口的支撐來治療應力性尿失禁，然後再以药物或行為治療處理手術後仍有逼尿肌不穩定的部份病人。然而有些專家則主張先以葯物或行為治療解決逼尿肌不穩定的部份，保留手術給急迫性尿失禁控制後仍有惱人的應力性尿失禁的病人。然而至今我們仍然無法分辨那些病人最適合立即接受手術治療，而那些則只要非手術的療法即可。另外，尿道逼尿肌促進反射是否存在人類，仍未獲得證實。
近年來，很多非腎上腺素非膽鹼性 (non-adrenergic non-cholinergic,NANC) 的神經傳導物質在下泌尿道生理弁鄐W扮演重要的角色。其中一氧化氮 (nitric oxide) 被證實在很多動物包括人類的下泌尿道造成尿肌平滑肌放鬆和尿道張力降低。抑鈣素基因相關胜肽(calcitonin-gene-related-peptide) 一直是尿道傳入神經作用的重要介質。去年更被證實經由動脈注射後可導致雌性大白鼠之最大尿道壓力下降65﹪之多。考量下泌尿道複雜的神經調控機轉，尿道逼尿肌促進反射，無法全盤性地解釋應力性尿失禁和急迫性尿失禁或逼尿肌不穩定的因果關係。
基於上述事實，我們認為研究近端尿道的抑鈣素基因相關胜肽(calcitonin-gene-related-peptide ,CGRP) 和 一氧化氮合成酶(nitric oxide synthase, NOS) 的含量，可能是瞭解混合型尿失禁的病理生理機轉的理想方法。
目的和方法
為了檢證我們的假説“混合型尿失禁的大白鼠在尿道的CGRP和eNOS的含量大於應力性尿失禁或正常禁尿弁鄋漱j白鼠”我們進行如下的實驗。總共有60隻第一次懷孕16天待產中的大白鼠，平均體重268.5公克進行實驗。所有動物生產完後立即進行第一次陰道內氣球擴張術，以模擬產道受傷。經飼養4週後再進行第二次擴張。第二次擴張後72小時進行尿路動力學檢查和噴嚏/壓力測試，以判定大白鼠尿失禁的狀況。緊接著犧牲實驗動物，並立即取下下泌尿道組織進行免疫組織化學研究，評估近端尿道CGRP和eNOS的含量。
結果
有五隻動物在實驗過程中因感染死亡。剩下55隻，其中25隻有混合型尿失禁（A組），20隻應力性尿失禁（B組），10隻正常禁尿弁遄]C組）。其中CGRP的含量分別是141.96 ±94.02個，52.37 ±26.58個, 23.46 ±10.97個。而eNOS則分別為17.57 ±11.12個，8.24 ±6.08個，2.38 ±1.36個。以CGRP和eNOS在尿道的含量而言，三組之間的差異皆達到統計上顯著的程度。至於三組的平均膀胱容量皆為1.5cc，並無差異。
結論
從我們實驗的結果顯示近端尿道CGRP和eNOS的含量和混合型尿失禁有很強的關聯性。這些發現暗示CGRP和eNOS的抑制劑可能是治療混合型尿失禁的另一新策略。
1. Background
The condition of mixed urinary incontinence (genuine stress urinary incontinence and urge urinary incontinence in the same patient) has long been a subject of therapeutic controversy. Some experts argue that many women with mixed urinary incontinence have stress urinary incontinence as the primary problem and that the urge urinary incontinence or detrusor instability ensues when the incompetent bladder neck allows urine to be forced into the proximal urethra during physical activity and exerting abdominal straining. The hypothesis therefore emerged that urethrodetrusor facilitative reflexes trigger an involuntary detrusor contraction. Based on this opinion they advocate primary operative correction of bladder outlet support, reserving pharmacological and behavioral therapy for those who have persistent urge urinary incontinence or detrusor instability after operation.
On the contrary, others advocate first treating the instability component( pharmacologically and/or behaviorally) and reserving operative management for those patients who have bothersome stress urinary incontinence after urge urinary incontinence or detrusor instability has been controlled. However, we to date have no way of telling patients with mixed urinary incontinence who would be best treated with initial operative management from those who would be best served with non-surgical interventions.
Besides, there is no conclusive evidence that urethrodetrusor facilitative reflex do exist in human beings. Recently, several nonadrenergic-nonchlinergic(NANC) mediators have been recognized to play a significant role in the physiology of the lower urinary tract. Nitric oxide(NO) has increasingly gained recognition as an important cell mediator in the lower urinary tract. It is considered to be an inhibitory NANC neurotransmitter causing urethral smooth muscle relaxation to reduce urethral tone in the lower urinary tract of different animal species, including humans. CGRP(calcitonin-gene-related-peptide) has long been recognized as a mediator involved in the urethral afferents pathway and was found out to have decreased 65% of maximal urethral pressure(MUP) while it was administered intra-arterially close to the bladder in female rats.
Considering the complex neural mechanism of lower urinary tract function, urine leakage eliciting stimulation of urethral afferents could not holistically explain the causative relationship between stress urinary incontinence and urge urinary incontinence or detrusor instability, both of them taking place in the same patient. To study the density of CGRP and NOS receptors in the proximal urethra can be a good way to shed light on the pathophysiology of mixed urinary incontinence. We sought experimental support that CGRP and NOS play a significant role in the pathophysiology of mixed urinary incontinence.
2. Aims, Materials and Methods
Our hypothesis comes out as “ The density of CGRP and NOS receptors in the proximal urethra must be higher in rats with mixed urinary incontinence than in those with pure stress urinary incontinence or normal continence.
A total of 60 primiparous pregnant Sprague-Dawley rats at gestation day 16 with a mean boy weight of 268.5 gm were obtained from the vendor. Immediately after delivery all animals underwent the first session of intravaginal balloon inflation simulating birth trauma. The second session was performed 4 weeks later. Cystometry and sneeze/stress test were done for all animals to sort out the continence status in each rat 72 hours after the second session of intravaginal balloon inflation. Following the urodynamic study, all animals were sacrificed. The lower urinary tract was then removed and processed for further evaluation with immunohistochemical stains to assess the number of CGRP and NOS receptors in the proximal urethra.
3. Results
5 rats were dead in the process of experiment. The continence status of the remaining 55 rats was mixed urinary incontinence in 25(Group A), stress urinary incontinence in 20(Group B), and normal continence in 10(Group C). The number of submucosal CGRP receptors of these three groups was 141.96±94.02(Group A), 52.37±26.58(Group B), and 23.46±10.97(Group C). The number of urothelial eNOS receptors among these 3 groups was 17.57±11.12(Group A), 8.24±6.08(Group B), 2.38±1.36(Group C). The difference between A&C, B&C, and A&B in terms of the number of both CGRP and eNOS receptors was all statistically significant.
4. Conclusions
The results indicate that the content of CGRP and eNOS in proximal urethra has a strong association with mixed urinary incontinence. These findings have significant implications for the treatment of patients with mixed urinary incontinence that inhibitors of CGRP and/or NOS may play a pivotal role and further research is mandatory.
Subjects
混合型尿失禁
一氧化氮合成酶
抑鈣素基因相關胜肽
Calcitonin-gene-related-peptide
Mixed urinary incontinence
Nitric oxide synthase
Type
text
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