Su Xiaoling, Stein Raymund, Stanton Michaela C, Zderic Stephen, Moreland Robert S
Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia 19102, USA.
Am J Physiol Renal Physiol. 2003 Apr;284(4):F644-52. doi: 10.1152/ajprenal.00274.2002. Epub 2002 Dec 27.
Bladder outlet obstruction secondary to benign prostate hyperplasia is associated with many cellular changes. This study was designed to determine whether these changes involve the contractile apparatus. Bladder smooth muscles from rabbits subjected to partial outlet obstruction for 2 wk were mounted for isometric force, isotonic shortening velocity, and myosin light chain (MLC) phosphorylation levels. Muscle strips from obstructed bladders exhibited spontaneous phasic activity; muscle strips from control bladders did not. Muscle strips from obstructed bladders exhibited increased sensitivity and higher levels of stress in response to the cumulative addition of KCl or carbachol compared with control. During noncumulative addition of KCl or carbachol, no differences in sensitivity were noted. Muscle strips from obstructed bladders had elevated basal MLC phosphorylation levels and stimulation produced small increases in MLC phosphorylation compared with control. V(max) during KCl stimulation of muscle strips from obstructed bladders was 10-fold lower than control. Our results suggest that bladder outlet obstruction produces a muscle cell that develops higher levels of force but with greatly reduced cross bridge cycling rates.
良性前列腺增生继发的膀胱出口梗阻与许多细胞变化相关。本研究旨在确定这些变化是否涉及收缩装置。将接受部分出口梗阻2周的兔膀胱平滑肌安装用于测量等长力、等张缩短速度和肌球蛋白轻链（MLC）磷酸化水平。梗阻膀胱的肌条表现出自发性阶段性活动；对照膀胱的肌条则没有。与对照相比，梗阻膀胱的肌条在累积添加氯化钾或卡巴胆碱时表现出更高的敏感性和更高的应激水平。在非累积添加氯化钾或卡巴胆碱期间，未观察到敏感性差异。与对照相比，梗阻膀胱的肌条基础MLC磷酸化水平升高，刺激后MLC磷酸化仅有小幅增加。梗阻膀胱肌条在氯化钾刺激期间的最大速度（Vmax）比对照低10倍。我们的结果表明，膀胱出口梗阻产生的肌细胞能产生更高水平的力，但横桥循环速率大大降低。
