Pagala M K, Tetsoti L, Nagpal D, Wise G J
Neuromuscular Research Laboratory, Division of Urology, Department of Surgery, Maimonides Medical Center, Brooklyn, New York 11219, USA.
J Urol. 2001 Aug;166(2):721-7.
Aging is associated with bladder dysfunction, including difficult voiding and urinary leakage. Voiding involves reduction in the bladder lumen in all dimensions brought about by contraction of the meshwork of longitudinal, circular and oblique layers of detrusor smooth muscles. Most in vitro physiological studies of the effects of aging on bladder function used the longitudinal detrusor. To understand the region specific effects of aging on bladder function the contractile responses of longitudinal and circular detrusor, and trigone segments of the bladder from young and old rats were monitored.
These studies were performed using male Fisher 344 rats 6 months (young) and 27 months (old) old obtained through the National Institute on Aging. Each rat was anesthetized and the bladder was isolated. From each bladder a strip of longitudinal detrusor, circular detrusor and trigone was isolated and mounted in an in vitro multi-muscle chamber containing normal physiological solution at 37C. Isometric contractions of the 3 bladder strips were monitored after electrical field stimulation, 120 mM. potassium and 1 to 1,000 microM. bethanechol using a digital oscilloscope.
In longitudinal detrusor from old rats there was no significant difference in the contractions evoked by electrical stimulation or high potassium but there was a significant reduction in contractions evoked by bethanechol compared with the responses of longitudinal detrusor from young rats. In circular detrusor from old rats there was a significant increase in contractions evoked by electrical stimulation and a slight increase in contractions produced by high potassium but no significant change in contractions evoked by bethanechol compared with the responses of circular detrusor from young rats. In trigone from old rats there was a significant decrease in contractions evoked by electrical stimulation, high potassium and bethanechol compared with young trigone.
The reduction in contractions evoked by bethanechol suggests an age related reduction in muscarinic receptors in the longitudinal detrusor of aged rats. An increase in contractions evoked by electrical stimulation without a change in contractions evoked by bethanechol suggests a decrease in compliance caused by an increase in collagen in the circular detrusor of aged rats. A general decline in all contractile responses, including those evoked by high potassium, suggests reduced membrane depolarization in the trigone of aged rats. The effect of aging is specific to different regions and functional components of the bladder, probably due to changes in muscarinic receptors, collagen and depolarization.
衰老与膀胱功能障碍相关，包括排尿困难和尿失禁。排尿涉及由逼尿肌平滑肌的纵向、环形和斜行层网络收缩引起的膀胱腔各维度的减小。大多数关于衰老对膀胱功能影响的体外生理学研究使用的是纵向逼尿肌。为了解衰老对膀胱功能的区域特异性影响，监测了年轻和老年大鼠膀胱的纵向和环形逼尿肌以及三角区的收缩反应。
这些研究使用的是通过美国国立衰老研究所获得的6个月大（年轻）和27个月大（老年）的雄性费希尔344大鼠。每只大鼠麻醉后分离出膀胱。从每个膀胱中分离出一条纵向逼尿肌、环形逼尿肌和三角区组织条，并将其安装在一个含有37℃正常生理溶液的体外多肌肉腔室中。使用数字示波器监测在电场刺激、120 mM钾和1至1000 μM氨甲酰甲胆碱作用下这3条膀胱组织条的等长收缩。
老年大鼠纵向逼尿肌在电刺激或高钾诱发的收缩方面无显著差异，但与年轻大鼠纵向逼尿肌的反应相比，氨甲酰甲胆碱诱发的收缩显著减少。老年大鼠环形逼尿肌在电刺激诱发的收缩方面显著增加，高钾诱发的收缩略有增加，但与年轻大鼠环形逼尿肌的反应相比，氨甲酰甲胆碱诱发的收缩无显著变化。与年轻三角区相比，老年大鼠三角区在电刺激、高钾和氨甲酰甲胆碱诱发的收缩方面显著减少。
氨甲酰甲胆碱诱发的收缩减少表明老年大鼠纵向逼尿肌中与年龄相关的毒蕈碱受体减少。电刺激诱发的收缩增加而氨甲酰甲胆碱诱发的收缩无变化表明老年大鼠环形逼尿肌中胶原蛋白增加导致顺应性降低。包括高钾诱发的收缩在内的所有收缩反应普遍下降表明老年大鼠三角区膜去极化减少。衰老的影响对膀胱的不同区域和功能成分具有特异性，可能是由于毒蕈碱受体、胶原蛋白和去极化的变化所致。
