Obstruction alters muscarinic receptor-coupled RhoA/Rho-kinase pathway in the urinary bladder of the rat

• Published in: Neurourology and urodynamics 2009-01, Vol.28 (3), p.257-262
• Main Authors: Takahashi, Norio, Shiomi, Homare, Kushida, Nobuhiro, Liu, Fei, Ishibashi, Kei, Yanagida, Tomohiko, Shishido, Keiichi, Aikawa, Ken, Yamaguchi, Osamu
• Format: Article
• Language: English
• Subjects: Amides - pharmacology; Animals; Blotting, Western; BOO; Ca2 sensitization; Carbachol - pharmacology; Electric Stimulation; Electrophoresis, Polyacrylamide Gel; Enzyme Inhibitors - pharmacology; In Vitro Techniques; Male; Muscarinic Agonists - pharmacology; Muscle Contraction - drug effects; Muscle Contraction - physiology; Muscle, Smooth - drug effects; Organ Size - drug effects; Pyridines - pharmacology; Rats; Rats, Sprague-Dawley; Receptors, Muscarinic - drug effects; Receptors, Muscarinic - physiology; rho GTP-Binding Proteins - biosynthesis; rho-Associated Kinases - antagonists & inhibitors; rho-Associated Kinases - drug effects; rho-Associated Kinases - physiology; Rho-kinase; Urinary Bladder - physiopathology; Urinary Bladder Neck Obstruction - physiopathology
• ISSN: 0733-2467; 1520-6777
• DOI: 10.1002/nau.20625

Aims The present study investigated the effects of the bladder outlet obstruction (BOO) on the muscarinic receptor (MR)‐coupled RhoA/Rho‐kinase (ROK) pathway in the detrusor smooth muscle of the rat. Methods Detrusor muscle samples were obtained from bladders after 4 weeks of BOO and also from sham‐operated control rats. Contractile responses to electrical field stimulation (EFS) and 1 μM carbachol (Cch) were determined in isolated detrusor strips. The effects of the ROK inhibitor Y‐27632 on the Cch‐induced phasic and sustained contractions were evaluated. Western blotting was used to determine the relative levels of RhoA expression and ROK isoform expression. Results Bladder weight increased significantly after 4 weeks of BOO. Contractile responses to EFS decreased significantly in detrusor muscle from the obstructed bladder. Cch (1 μM) induced a biphasic response consisting of an initial phasic contraction followed by a sustained contraction. Y‐27632 attenuated the phasic and sustained contractions induced by Cch in both control and obstructed bladders. However, BOO caused a significant increase in contractile force during the sustained phase of the contractions induced by Cch. An inhibitory effect of Y‐27632 on the sustained responses to Cch was significantly enhanced in the obstructed bladder. In accordance with the functional study, the expression of RhoA and ROK isoforms (both α and β) at the protein level significantly increased in the obstructed bladder. Conclusions These results suggest that the enhanced MR‐coupled RhoA/ROK pathway contributes to the maintenance of contractile force in the obstructed bladder, as a compensatory mechanism for expelling the urine against the obstruction. Neurourol. Urodynam. 28:257–262, 2009. © 2009 Wiley‐Liss, Inc.