title: Development of an in vitro model to measure bioactivity of botulinum neurotoxin A in rat bladder muscle strips.
abstract: BACKGROUND
  Botulinum toxin A (BoNT-A) is a new treatment modality in various causes of bladder dysfunction; like neurogenic detrusor overactivity and overactive bladder. The best technique of administrating BoNT-A in patients is unknown. A validated in vitro model could be used to investigate newer intravesical administration techniques of BoNT-A. In this study, we describe the development and validation of in vitro model to measure inhibitory effects of BoNT-A on bladder strip contractions.
  
  
  METHODS
  Rat bladder strips were mounted in organ baths filled with Krebs' solution. The strips were stimulated chemically (80 mM potassium chloride, 1 μM carbachol) and electrically (Electrical Field Stimulation (EFS) 100 shocks, 50 V, 20 Hz, every 3 minutes). The viability of the strips was measured by carbachol stimulation at the beginning and at the end of the experiments. The strips were incubated in various concentrations of BoNT-A (0.03, 0.2, 0.3 nM). Controls were incubated in Krebs' solution only. The inhibition of strip contraction induced by EFS was measured. These measurements were statistically analyzed with a log-logistic model representing diffusion.
  
  
  RESULTS
  All strips remained viable during the experiments. Inhibition of strip contraction was observed after incubation with 0.3 nM BoNT-A. The measurements fitted to a log-logistic model describing diffusion of BoNT-A in the bladder strip. The parameters of the log-logistic model representing diffusion were significant for 0.3 nM BoNT-A. Incubation with 0.2 nM BoNT-A showed insignificant results for 2 out of 3 runs. Incubation with 0.03 nM BoNT-A did not result in significant inhibition of strip contractions.
  
  
  CONCLUSIONS
  An in vitro model was developed and validated in which the inhibitory effect of low concentrations of BoNT-A on bladder strip contractions can be measured.
authors.affiliation: Department of Urology, VU University Medical Center, PO Box 7057, Amsterdam 1007 MB, The Netherlands. j_vanuhm@hotmail.com.
authors.forename: Janneke I M
authors.initials: JI
authors.lastname: van Uhm
authors.forename: Goedele M A
authors.initials: GM
authors.lastname: Beckers
authors.forename: Willem J
authors.initials: WJ
authors.lastname: van der Laarse
authors.forename: Eric J H
authors.initials: EJ
authors.lastname: Meuleman
authors.forename: Albert A
authors.initials: AA
authors.lastname: Geldof
authors.forename: Jakko A
authors.initials: JA
authors.lastname: Nieuwenhuijzen
mesh_terms: D000818:Animals; D001681:Biological Assay / Q000379:methods; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical / Q000379:methods; D066298:In Vitro Techniques; D008297:Male; D023421:Models, Animal; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects* / Q000502:physiology*; D009465:Neuromuscular Agents / Q000008:administration & dosage; D051381:Rats; D017208:Rats, Wistar; D001743:Urinary Bladder / Q000187:drug effects* / Q000502:physiology*
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A