title: Enhancement of ventricular gap-junction coupling by rotigaptide.
abstract: OBJECTIVE
  Rotigaptide is proposed to exert its anti-arrhythmic effects by improving myocardial gap-junction communication. To directly investigate the mechanisms of rotigaptide action, we treated cultured neonatal murine ventricular cardiomyocytes with clinical pharmacological doses of rotigaptide and directly determined its effects on gap-junctional currents.
  
  
  RESULTS
  Neonatal murine ventricular cardiomyocytes were enzymatically isolated and cultured for 1-4 days. Primary culture cell pairs were subjected to dual whole cell patch-clamp procedures to directly measure gap-junctional currents (I(j)) and voltage (V(j)). Rotigaptide (0-350 nM) was applied overnight or acutely perfused into 35 mm culture dishes. Rotigaptide (35-100 nM) acutely and chronically increased the resting gap-junction conductance (g(j)), and normalized steady-state minimum g(j) (G(min)) by 5-20%. Higher concentrations produced a diminishing response, which mimics the observed therapeutic efficacy of the drug. The inactivation kinetics was similarly slowed in a therapeutic concentration-dependent manner without affecting the V(j) dependence of inactivation or recovery. The effects of 0-100 nM rotigaptide on ventricular g(j) during cardiac action potential propagation were accurately modelled by computer simulations which demonstrate that clinically effective concentrations of rotigaptide can partially reverse conduction slowing due to decreases in g(j) and inactivation.
  
  
  CONCLUSIONS
  These results demonstrate that therapeutic concentrations of rotigaptide increase the resting gap-junction conductance and reduce the magnitude and kinetics of steady-state inactivation in a concentration-dependent manner. Rotigaptide may be effective in treating re-entrant forms of cardiac arrhythmias by improving conduction and preventing the formation of re-entrant circuits in partially uncoupled myocardium.
authors.affiliation: Department of Pharmacology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
authors.forename: Xianming
authors.initials: X
authors.lastname: Lin
authors.forename: Christian
authors.initials: C
authors.lastname: Zemlin
authors.forename: James K
authors.initials: JK
authors.lastname: Hennan
authors.forename: Jørgen S
authors.initials: JS
authors.lastname: Petersen
authors.forename: Richard D
authors.initials: RD
authors.lastname: Veenstra
mesh_terms: D000200:Action Potentials; D000818:Animals; D000831:Animals, Newborn; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D002450:Cell Communication / Q000187:drug effects*; D002478:Cells, Cultured; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D017629:Gap Junctions / Q000187:drug effects* / Q000378:metabolism; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008955:Models, Cardiovascular; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology*
chemical_list: D000889:Anti-Arrhythmia Agents; D009842:Oligopeptides; C477643:rotigaptide