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和缺血相关病理变化的良好模型。为了阐明缺血到膀胱功能障碍的过程，我们观察了WHHL兔膀胱的组织学、生理学和药理学变化。材料和方法：雄性WHHL兔分为3个年龄组(6月龄：6月龄、12月龄：12月龄和24月龄：24月龄)和年龄和性别匹配的日本大白兔(对照组)。连续测量每只兔的排尿次数和每次尿量，连续3天。然后进行充盈性膀胱测压。处死后取膀胱进行HE染色和S-100蛋白、降钙素基因相关肽神经元免疫组织化学染色。此外，在脏器浴中悬吊膀胱平滑肌条，并用卡巴胆碱、Kc1(80 MM)a…引起的收缩对更多的电场刺激进行评估。结果：12、24M龄WHHL兔排尿次数明显多于对照组，排尿量显著低于对照组。在对照组中，组织氧合在组间无显著差异。在WHHL兔中，随着年龄的增长，膀胱组织氧合显著降低。12M龄WHHL兔的膀胱计量学结果显示，与对照组相比，无排尿收缩，排尿间隔缩短，尿量减少。24M龄WHHL兔上述异常表现加重。在功能研究中，卡巴胆碱和EFS对6和12M龄WHHL兔的收缩反应均显著高于对照组。然而，在24只M WHHL兔中，这种反应显著降低。在WHHL组，S-100蛋白阳性神经元的密度随年龄的增长而显著降低。而12、24M龄WHHHL兔CGRP阳性神经元密度明显增加。WHHL组神经元ACh和ATP释放明显减少。牵张诱导的非神经元性ACh和ATP在WHHL组显著升高。结论：WHHL兔存在缺血所致的膀胱功能障碍。在膀胱缺血的早期，平滑肌对神经递质的反应增强可能是逼尿肌过度活动的原因之一。在慢性期，传入神经元的激活也可能是逼尿肌过度活动的原因之一。此外，逼尿肌活动不足的原因是平滑肌面积减少，对神经递质的反应性降低，这可能是由于神经递质释放减少所致。较少

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