Blebbistain, a myosin II inhibitor, as a novel strategy to regulate detrusor contractility in a rat model of partial bladder outlet obstruction

PLoS One. 2011;6(10):e25958. doi: 10.1371/journal.pone.0025958. Epub 2011 Oct 7.


Partial bladder outlet obstruction (PBOO), a common urologic pathology mostly caused by benign prostatic hyperplasia, can coexist in 40-45% of patients with overactive bladder (OAB) and is associated with detrusor overactivity (DO). PBOO that induces DO results in alteration in bladder myosin II type and isoform composition. Blebbistatin (BLEB) is a myosin II inhibitor we recently demonstrated potently relaxed normal detrusor smooth muscle (SM) and reports suggest varied BLEB efficacy for different SM myosin (SMM) isoforms and/or SMM vs nonmuscle myosin (NMM). We hypothesize BLEB inhibition of myosin II as a novel contraction protein targeted strategy to regulate DO. Using a surgically-induced male rat PBOO model, organ bath contractility, competitive and Real-Time-RT-PCR were performed. It was found that obstructed-bladder weight significantly increased 2.74-fold while in vitro contractility of detrusor to various stimuli was impaired ∼50% along with decreased shortening velocity. Obstruction also altered detrusor spontaneous activities with significantly increased amplitude but depressed frequency. PBOO switched bladder from a phasic-type to a more tonic-type SM. Expression of 5' myosin heavy chain (MHC) alternatively spliced isoform SM-A (associated with tonic-type SM) increased 3-fold while 3' MHC SM1 and essential light chain isoform MLC(17b) also exhibited increased relative expression. Total SMMHC expression was decreased by 25% while the expression of NMM IIB (SMemb) was greatly increased by 4.5-fold. BLEB was found to completely relax detrusor strips from both sham-operated and PBOO rats pre-contracted with KCl, carbachol or electrical field stimulation although sensitivity was slightly decreased (20%) only at lower doses for PBOO. Thus we provide the first thorough characterization of the response of rat bladder myosin to PBOO and demonstrate complete BLEB-induced PBOO bladder SM relaxation. Furthermore, the present study provides valuable evidence that BLEB may be a novel type of potential therapeutic agent for regulation of myogenic and nerve-evoked DO in OAB.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Carbachol / pharmacology
  • Disease Models, Animal
  • Gene Expression Regulation / drug effects
  • Heterocyclic Compounds, 4 or More Rings / pharmacology*
  • In Vitro Techniques
  • Male
  • Muscle Contraction / drug effects*
  • Muscle Relaxation / drug effects
  • Muscle, Smooth / drug effects*
  • Muscle, Smooth / metabolism
  • Muscle, Smooth / physiopathology*
  • Myosin Type II / antagonists & inhibitors*
  • Myosin Type II / genetics
  • Myosin Type II / metabolism
  • Protein Isoforms / metabolism
  • Rats
  • Urinary Bladder / drug effects
  • Urinary Bladder / metabolism
  • Urinary Bladder / physiopathology
  • Urinary Bladder Neck Obstruction / genetics
  • Urinary Bladder Neck Obstruction / metabolism
  • Urinary Bladder Neck Obstruction / physiopathology*


  • Heterocyclic Compounds, 4 or More Rings
  • Protein Isoforms
  • blebbistatin
  • Carbachol
  • Myosin Type II