Ca2+ sensitization in contraction of human bladder smooth muscle.
OBJECTIVE
The role of Ca2+ sensitization in the contraction of human bladder urinary smooth muscle (UBSM) was investigated.


METHODS
Simultaneous measurements of intracellular Ca2+ concentration ([Ca2+]i) and tension in fura-2 loaded intact strips and receptor coupled strips permeabilized with alpha-toxin were applied. Protein expressions was confirmed by Western blot analysis.


RESULTS
In intact fura-2 loaded strips 1 microM carbachol (CCh) induced a greater contraction and a lower [Ca2+]i elevation than that induced by 60 mM K depolarization. In alpha-toxin permeabilized strips 1 microM CCh induced contraction at constant [Ca2+]i and produced a leftward shift in the [Ca2+]i-tension relationship. RhoA, Rho-associated kinase (ROCK) I, ROCK II and CPI-17 proteins were expressed in human UBSM. In intact fura-2 loaded strips the application of 3 microM Y-27632, a ROCK inhibitor, or 3 microM bisindolylmaleimide I (GF109203X), a protein kinase C inhibitor, during the sustained phase of contraction induced by 1 microM CCh induced relaxation without changing [Ca2+]i. In alpha-toxin permeabilized strips the application of 3 microM Y-27632 or 3 microM GF109203X during the sustained contraction induced by 0.3 microM Ca plus 10 microM guanosine triphosphate and 1 microM CCh induced relaxation at constant [Ca2+]i.


CONCLUSIONS
These results indicate that in human UBSM CCh induces contraction, not only by increasing [Ca2+]i, but also by increasing the Ca2+ sensitivity of the contractile apparatus in a ROCK and protein kinase C dependent manner. Antagonism of Ca2+ sensitization pathways may represent an alternative target in the treatment of overactive bladder.
Takahashi
Ryosuke
R
Division of Molecular Cardiology, Research Institute of Angiocardiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
Nishimura
Junji
J
Hirano
Katsuya
K
Seki
Narihito
N
Naito
Seiji
S
Kanaide
Hideo
H
D000368:Aged; D000577:Amides / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D009119:Muscle Contraction / Q000502:physiology*; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D009130:Muscle, Smooth / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D001743:Urinary Bladder / Q000166:cytology / Q000502:physiology; D054460:rho-Associated Kinases
D000577:Amides; D007211:Indoles; D047908:Intracellular Signaling Peptides and Proteins; D008301:Maleimides; D009125:Muscle Relaxants, Central; D011725:Pyridines; C108830:Y 27632; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D011493:Protein Kinase C; C070515:bisindolylmaleimide I; D002118:Calcium