title: Effect of the SK/IK channel modulator 4,5-dichloro-1,3-diethyl-1,3-dihydro-benzoimidazol-2-one (NS4591) on contractile force in rat, pig and human detrusor smooth muscle.
abstract: OBJECTIVE
  • To investigate the importance of small (SK)- and intermediate (IK)-conductance Ca2(+) -activated K(+) channels on bladder function, by studying the effects of 4,5-dichloro-1,3-diethyl-1,3-dihydro-benzoimidazol-2-one (NS4591), a new modulator of SK/IK channels, on contractions induced by electrical field stimulation (EFS) and carbachol in rat, pig and human detrusor.
  
  
  METHODS
  • Detrusor biopsies were obtained from rats, pigs and male patients undergoing cystectomy because of bladder cancer. • Force was recorded using myographs. • Intracellular free Ca(2+) was measured in myocytes using microfluorimetry.
  
  
  RESULTS
  • In rat bladder rings subjected to EFS, cumulative addition of NS4591 (0.1-30 µM) decreased force by 82 ± 2.9% (n = 6).This effect was reduced by 64 ± 5.2% in the presence of 0.3 µM apamin, a specific inhibitor of SK channels. Apamin increased the force evoked by EFS significantly: force was increased by 14.2 ± 3.4% (n = 5) and 10.1 ± 2.6% (n = 7) in pig and human detrusor strips, respectively (P = 0.04 and P = 0.02). • The cumulative addition of NS4591 (0.3-30 µM) significantly reduced the amplitude of carbachol-induced rhythmic oscillations by 62.0 ± 12.0% (n = 12) and the minimum force between oscillations by 30 ± 5% (n = 9) in pig detrusor strips (P < 0.005). In the presence of 10 µM NS4591, carbachol (1 µM) induced rhythmic contractions with an amplitude and normalized mean power frequency (nmeanPF) of 8.4 ± 5.1% and 0.11 ± 0.06 mN root mean square (rms) Hz (n = 12), respectively, vs. 21 ± 3.4% and 0.17 ± 0.04 mN rms Hz in control strips (n = 13). Apamin induced 6- and 11-fold increases in amplitude and nmeanPF vs. 1.3- and 2-fold increases in control strips. • In human detrusor strips (n = 15), the cumulative addition of NS4591 (1-30 µM) significantly reduced the amplitude by 69 ± 11%, the nmeanPF by 78 ± 6% and the minimum force between carbachol-induced oscillations by 59 ± 5% (P < 0.008). The addition of apamin (0.3 µM) before application of 1 µM carbachol abolished the effects of NS4591 on amplitude and partially abolished its effect on nmeanPF by 41 ± 7%, vs. a 78 ± 6% reduction in the absence of apamin (n = 8). • In spontaneously active detrusor preparations, NS4591 reduced or abolished contractions. • Furthermore, NS4591 (10 µM) decreased the carbachol-induced increase in the fura-2 ratio by 43 ± 3% compared with control (n = 12) (P < 0.03).
  
  
  CONCLUSIONS
  • The SK/IK channel modulator NS4591 inhibits EFS- and carbachol-induced contractions in rat, pig and human detrusor muscle. • NS4591 may have therapeutic potential for treatment of detrusor overactivity.
authors.affiliation: Smooth Muscle Research Center, Koege Hospital, Herlev, Denmark.
authors.forename: Jens Steen
authors.initials: JS
authors.lastname: Nielsen
authors.forename: Frederik
authors.initials: F
authors.lastname: Rode
authors.forename: Mette
authors.initials: M
authors.lastname: Rahbek
authors.forename: Karl-Erik
authors.initials: KE
authors.lastname: Andersson
authors.forename: Lars Christian
authors.initials: LC
authors.lastname: Rønn
authors.forename: Kirsten
authors.initials: K
authors.lastname: Bouchelouche
authors.forename: Jorgen
authors.initials: J
authors.lastname: Nordling
authors.forename: Pierre
authors.initials: P
authors.lastname: Bouchelouche
mesh_terms: D000368:Aged; D000818:Animals; D001562:Benzimidazoles / Q000494:pharmacology*; D015653:Cystectomy; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051640:Small-Conductance Calcium-Activated Potassium Channels / Q000494:pharmacology*; D013552:Swine; D001743:Urinary Bladder / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D001749:Urinary Bladder Neoplasms / Q000601:surgery
chemical_list: C534785:4,5-dichloro-1,3-diethyl-1,3-dihydrobenzoimidazol-2-one; D001562:Benzimidazoles; D026902:Potassium Channel Blockers; D051640:Small-Conductance Calcium-Activated Potassium Channels