Kim Y S, Wang Z, Levin R M, Chacko S
Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104.
Mol Cell Biochem. 1994 Feb 23;131(2):115-24. doi: 10.1007/BF00925947.
The obstruction of the bladder outlet induces a marked increase in bladder mass, and this is accompanied by reduced contractility of bladder smooth muscle and alteration in the cellular architecture. In this study, we show that the composition of various isoforms of actin, a major component of the contractile apparatus and the cytoskeletal structure of smooth muscle, is altered in response to the obstruction-induced bladder hypertrophy. Northern blot analysis of the total RNA isolated from hypertrophied urinary bladder muscle, using a cDNA probe specific for smooth muscle gamma-actin, shows over 200% increase in the gamma-actin mRNA. However, the estimate of the amount of actin from the 2D gel reveals only a 16% increase in gamma-actin, since the 2D gel electrophoresis does not distinguish gamma-smooth muscle actin from gamma-cytoplasmic actin. The bladder smooth muscle alpha-actin and the smooth muscle alpha-actin mRNA are not altered in response to the hypertrophy. The obstructed bladder also reveals a decrease in the beta-cytoplasmic actin (37%) and a concomitant diminution in the beta-cytoplasmic actin mRNA (29%). Hence, the composition of the actin isoforms in bladder smooth muscle is altered in response to the obstruction-induced hypertrophy. This alteration of the actin isoforms is observed at both the protein and mRNA levels.
膀胱出口梗阻导致膀胱重量显著增加，同时伴有膀胱平滑肌收缩力降低和细胞结构改变。在本研究中，我们发现，作为收缩装置和平滑肌细胞骨架结构主要成分的肌动蛋白各种同工型的组成，会因梗阻诱导的膀胱肥大而发生改变。使用平滑肌γ-肌动蛋白特异性cDNA探针，对从肥大膀胱肌肉中分离的总RNA进行Northern印迹分析，结果显示γ-肌动蛋白mRNA增加超过200%。然而，二维凝胶电泳对肌动蛋白含量的估计显示，γ-肌动蛋白仅增加了16%，因为二维凝胶电泳无法区分γ-平滑肌肌动蛋白和γ-细胞质肌动蛋白。膀胱平滑肌α-肌动蛋白及其mRNA在肥大反应中未发生改变。梗阻膀胱的β-细胞质肌动蛋白也减少了37%，同时β-细胞质肌动蛋白mRNA减少了29%。因此，膀胱平滑肌中肌动蛋白同工型的组成因梗阻诱导的肥大而发生改变。这种肌动蛋白同工型的改变在蛋白质和mRNA水平均有观察到。
