title: Effects of Rho-kinase inhibition on myosin light chain phosphorylation and obstruction-induced detrusor overactivity.
abstract: OBJECTIVE
  To study the relationship between myosin light chain phosphorylation of the detrusor muscle and spontaneous smooth muscle contractions in a rabbit model of partial outlet obstruction.
  
  
  METHODS
  New Zealand white rabbit urinary bladders were partially obstructed for 2 weeks. Rabbits were euthanized, detrusor muscle strips were hung on a force transducer and spontaneous activity was measured at varying concentrations (0-0.03 μM/L) of the Rho-kinase inhibitors GSK 576371 or 0.01 μM/L Y27632. Basal myosin light chain phosphorylation was measured by 2-D gel electrophoresis in control and GSK 576371-treated strips.
  
  
  RESULTS
  Both drugs suppressed the force of spontaneous contractions, whereas GSK 576371 had a more profound effect on the frequency of the contractions. The IC₅₀ values for the inhibition of frequency and force of spontaneous contractions were 0.17 μM/L and 0.023 μM/L for GSK 576371, respectively. The compound significantly decreased the basal myosin light chain phosphorylation from 28.0 ± 3.9% to 13.5 ± 1.9% (P < 0.05). At 0.01 μM/L, GSK 576371 inhibited spontaneous bladder overactivity by 50%, but inhibited carbachol-elicited contractions force by just 25%.
  
  
  CONCLUSIONS
  These data suggest that Rho-kinase regulation of myosin light chain phosphorylation contributes to the spontaneous detrusor activity induced by obstruction. This finding could have therapeutic implications by providing another therapeutic option for myogenic, overactive bladder.
authors.affiliation: School of Veterinary Medicine, University of Pennsylvania, Philadelphia, USA.
authors.forename: James O
authors.initials: JO
authors.lastname: Marx
authors.forename: Maureen E
authors.initials: ME
authors.lastname: Basha
authors.forename: Sunish
authors.initials: S
authors.lastname: Mohanan
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hypolite
authors.forename: Shaohua
authors.initials: S
authors.lastname: Chang
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Wein
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Zderic
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Laping
authors.forename: Samuel
authors.initials: S
authors.lastname: Chacko
mesh_terms: D000818:Animals; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D008297:Male; D008969:Molecular Sequence Data; D018994:Myosin Light Chains / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011817:Rabbits; D001748:Urinary Bladder Neck Obstruction / Q000150:complications; D053201:Urinary Bladder, Overactive / Q000209:etiology / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors*
chemical_list: D004791:Enzyme Inhibitors; D018994:Myosin Light Chains; D054460:rho-Associated Kinases
keywords: Rho-kinase inhibitor; myosin phosphorylation; outlet obstruction; spontaneous contraction