Study in the pathophysiology of overactive bladder-Effects of bladder ischemia and hyperlipidemia

研究目的：渡边遗传性高脂血症（WHHL）兔有动脉粥样硬化病变。据报道，WHHL兔是研究动脉粥样硬化发生发展及缺血相关病理改变的良好模型。为了阐明缺血-膀胱功能障碍的过程，我们对WHHL兔膀胱的组织学、生理和药理变化进行了评价。材料与方法：选取6月龄6 M、12月龄12 M、24月龄24 M的WHHL雄性兔和年龄、性别匹配的日本大白兔作为对照组。连续3 d测量每只家兔的排尿次数和每次排尿量。然后行膀胱充盈术。牺牲后取膀胱进行HE染色、S-100蛋白和CGRP神经元免疫组化染色。另外，将膀胱平滑肌条悬挂于脏器浴中，观察甲胆碱、KC1（80 mM）、KC1（80 mM）和电场刺激对膀胱平滑肌的收缩作用。用微透析方法测定两组神经元和非神经元乙酰胆碱和ATP的释放。结果：12、24 M龄WHHL家兔排尿次数和排尿量均显著高于对照组，排尿量显著低于对照组。对照组组织氧合水平组间差异无统计学意义。WHHL家兔膀胱组织氧合明显随年龄下降。12 M龄WHHL家兔膀胱测量结果显示，与对照组相比，非排尿性收缩，排尿间隔缩短，排尿量减少。在24 M龄WHHL兔中，异常表现加重。在功能研究中，与对照组相比，6和12 M龄WHHL家兔经甲醇和EFS诱导的收缩明显增强。然而，24 M WHHL兔的反应明显消失。WHHL组大鼠S-100蛋白阳性神经元密度随年龄增长而显著降低。12、24 M龄WHHHL兔CGRP阳性神经元密度显著增加。WHHL组神经元乙酰胆碱和ATP释放量显著降低。拉伸诱导的非神经元性乙酰胆碱和ATP显著升高。结论：WHHL家兔存在缺血性膀胱功能障碍。在膀胱缺血的早期阶段，平滑肌对神经递质的反应性增加可能导致逼尿肌过度活动。在慢性期，传入神经元的激活也可能导致逼尿肌过度活动。此外，逼尿肌活动不足是由平滑肌面积减少和对神经递质反应性降低引起的，这可能是由神经递质释放减少引起的。少

Aims of study : Watanabe heritable hyperlipidemic(WHHL)rabbits have atherosclerotic lesions. It is reported that WHHL rabbit is a good model for study of the development and progression of atherosclerosis and the ischemia-related pathological changes. To clarify the process of ischemia-to bladder dysfunction, we evaluated the histological, physiological and pharmacological changes in bladder of WHHL rabbits.Materials and methods : Male WHHL rabbits in three age groups (6 months : 6 M, 12 months : 12 M and 24 months : 24 M) and the age and sex-matched Japanese white rabbits(control group)were used. Each rabbit was continuously measured the number of micturition and each micturition volume for 3 days. Then, filling cystometry was performed. After sacrifice, bladders were obtained for HE stainings and immunohistochemical stainings for S-100 protein and CGRP neurons. In addition, bladder smooth muscle strip was suspended in organ bath, and the contractions induced by carbachol, KC1(80 mM)a … More nd electrical field stimulation were evaluated. Neuronal and non-neuronal ACh and ATP release in both groups were measured using microdialysis procedure.Results : The number of micturition and voided volume in 12 and 24 M old WHHL rabbits were significantly higher and lower than that of the control, respectively. In the control groups, tissue oxygenation was not significant difference among groups. In WHHL rabbits, there was significant age-related decrease in bladder tissue oxygenation. Cystometric findings in 12 M old WHHL rabbits showed the non-voiding contractions, shorter interval micturition and lower micturition volume, as compared with the control. The abnormal findings worsened in the 24 M old WHHL rabbits. In the functional study, the contractions induce by carbachol and EFS in 6 and 12 M old WHHL rabbits significantly, increased, as compared with control. However, the responses significantly deceased in 24 M WHHL rabbits. In WHHL groups, the density of S-100 protein positive neuron significantly decreased with age. While, the density of CGRP positive neurons significantly increased in 12 and 24 M old WHHHL rabbits. Neuronal ACh and ATP releases in WHHL group significantly decreased. Stretch-induced non-neuronal ACh and ATP significantly increased in WHHL group.Conclusions : The data demonstrated the ischemia-induced bladder dysfunction in WHHL rabbits. In the early phase of bladder ischemia, increased smooth muscle responsiveness to neurotransmitters may contribute to detrusor overactivity. In the chronic phase, activation of afferent neurons may also contribute to the detrusor overactivity. Furthermore, detrusor underactivity was caused by decrease in smooth muscle area, and decreased responsiveness to neurotransmitters, which may be induced by decreased releases in neurotransmitters. Less