Obstruction alters muscarinic receptor-coupled RhoA/Rho-kinase pathway in the urinary bladder of the rat.
OBJECTIVE
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 microM 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 microM) 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 alpha and beta) 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.
Takahashi
Norio
N
Department of Urology, Fukushima Medical University, Fukushima, Japan. mudamuda@ohta-hp.or.jp
Shiomi
Homare
H
Kushida
Nobuhiro
N
Liu
Fei
F
Ishibashi
Kei
K
Yanagida
Tomohiko
T
Shishido
Keiichi
K
Aikawa
Ken
K
Yamaguchi
Osamu
O
D000577:Amides / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002217:Carbachol / Q000494:pharmacology; D004558:Electric Stimulation; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000502:physiology*; D001743:Urinary Bladder / Q000503:physiopathology*; D001748:Urinary Bladder Neck Obstruction / Q000503:physiopathology*; D020741:rho GTP-Binding Proteins / Q000096:biosynthesis; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000502:physiology*
D000577:Amides; D004791:Enzyme Inhibitors; D018721:Muscarinic Agonists; D011725:Pyridines; D011976:Receptors, Muscarinic; C108830:Y 27632; D002217:Carbachol; D054460:rho-Associated Kinases; D020741:rho GTP-Binding Proteins