Lemack G E, Zimmern P E, Vazquez D, Connell J D, Lin V K
Department of Urology, University of Texas - Southwestern Medical Center, Dallas, Texas, USA.
J Urol. 2000 Jun;163(6):1981-7.
Following prolonged partial bladder outlet obstruction (BOO) in the mouse, cholinergic mediated detrusor contractility decreases. Previous work has demonstrated an increase in the inducible form of nitric oxide synthase (iNOS) at the mRNA and protein levels soon after obstruction. Since nitric oxide (NO), the product of the action of iNOS on molecular oxygen and l-arginine, produces vasodilation and decreases platelet aggregation, we believe it is an integral part of the initial detrusor response to obstruction. These experiments evaluated the detrusor response in mice incapable of producing iNOS.
Wild type and knockout mice were partially obstructed for 1, 3, and 5 weeks. Physiologic evaluation consisted of cystometric analyses, and muscle strip studies in response to cholinergic and electrical stimulation. Strips were also relaxed with L-arginine, sodium nitroprusside, and 8-bromoguanosine 3' - 5' cyclic GMP, after precontraction.
After 5 weeks of obstruction, both wild type (WT) and knockout (KO) mouse bladders increased significantly in weight. WT bladders obstructed for 5 weeks had the greatest capacity (increase of 42%, p = 0.022), and a decreased contractile response to carbachol (decrease of 32% at 10-5 M, p = 0.018). No differences were noted at 1 and 3 weeks of obstruction. In contrast, KO mice had a significantly larger bladder capacity at 1 week of obstruction compared with WT, and had significantly lower responses to electrical stimulation than WT at the same time (p = 0.03). Additionally, after 5 weeks of obstruction, bladder capacity and contractility returned to baseline levels in KO mice, at a time when WT mice had significantly larger capacity and decreased contractility.
Bladder function following partial BOO in mice incapable of producing iNOS differed significantly from the normal response. Our data suggest that generation of iNOS soon after obstruction is necessary to prevent detrusor dysfunction at that time. Moreover, the enhanced function seen in KO bladders after longer periods of obstruction (5 weeks) in comparison to WT bladders suggests that reactive nitrogen species-induced protein nitrosylation may be involved in the loss of contractile function observed after more prolonged periods of obstruction.
在小鼠出现长期部分膀胱出口梗阻（BOO）后，胆碱能介导的逼尿肌收缩力会下降。先前的研究表明，梗阻后不久，诱导型一氧化氮合酶（iNOS）的mRNA和蛋白质水平会升高。由于一氧化氮（NO）是iNOS作用于分子氧和L-精氨酸的产物，可产生血管舒张并减少血小板聚集，我们认为它是逼尿肌对梗阻初始反应的一个组成部分。这些实验评估了无法产生iNOS的小鼠的逼尿肌反应。
野生型和基因敲除小鼠被部分梗阻1、3和5周。生理评估包括膀胱测压分析以及对胆碱能和电刺激的肌条研究。在预收缩后，肌条还分别用L-精氨酸、硝普钠和8-溴鸟苷3'-5'环鸟苷酸进行舒张实验。
梗阻5周后，野生型（WT）和基因敲除（KO）小鼠的膀胱重量均显著增加。梗阻5周的WT膀胱容量最大（增加42%，p = 0.022），对卡巴胆碱的收缩反应降低（在10-5 M时降低32%，p = 0.018）。在梗阻1周和3周时未观察到差异。相比之下，KO小鼠在梗阻1周时的膀胱容量显著大于WT，且在同一时间对电刺激的反应显著低于WT（p = 0.03）。此外，梗阻5周后，KO小鼠的膀胱容量和收缩力恢复到基线水平，而此时WT小鼠的膀胱容量显著更大且收缩力降低。
无法产生iNOS的小鼠在部分BOO后的膀胱功能与正常反应有显著差异。我们的数据表明，梗阻后不久iNOS的产生对于预防当时的逼尿肌功能障碍是必要的。此外，与WT膀胱相比，KO膀胱在更长时间梗阻（5周）后出现的功能增强表明，活性氮物种诱导的蛋白质亚硝化作用可能与更长时间梗阻后观察到的收缩功能丧失有关。
