title: Repolarizing K+ currents ITO1 and IKs are larger in right than left canine ventricular midmyocardium.
abstract: BACKGROUND
  The ventricular action potential exhibits regional heterogeneity in configuration and duration (APD). Across the left ventricular (LV) free wall, this is explained by differences in repolarizing K+ currents. However, the ionic basis of electrical nonuniformity in the right ventricle (RV) versus the LV is poorly investigated. We examined transient outward (ITO1), delayed (IKs and IKr), and inward rectifier K+ currents (IK1) in relation to action potential characteristics of RV and LV midmyocardial (M) cells of the same adult canine hearts.
  
  
  RESULTS
  Single RV and LV M cells were used for microelectrode recordings and whole-cell voltage clamping. Action potentials showed deeper notches, shorter APDs at 50% and 95% of repolarization, and less prolongation on slowing of the pacing rate in RV than LV. ITO1 density was significantly larger in RV than LV, whereas steady-state inactivation and rate of recovery were similar. IKs tail currents, measured at -25 mV and insensitive to almokalant (2 micromol/L), were considerably larger in RV than LV. IKr, measured as almokalant-sensitive tail currents at -50 mV, and IK1 were not different in the 2 ventricles.
  
  
  CONCLUSIONS
  Differences in K+ currents may well explain the interventricular heterogeneity of action potentials in M layers of the canine heart. These results contribute to a further phenotyping of the ventricular action potential under physiological conditions.
authors.affiliation: Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University, The Netherlands. p.volders@cardio.azm.nl
authors.forename: P G
authors.initials: PG
authors.lastname: Volders
authors.forename: K R
authors.initials: KR
authors.lastname: Sipido
authors.forename: E
authors.initials: E
authors.lastname: Carmeliet
authors.forename: R L
authors.initials: RL
authors.lastname: Spätjens
authors.forename: H J
authors.initials: HJ
authors.lastname: Wellens
authors.forename: M A
authors.initials: MA
authors.lastname: Vos
mesh_terms: D000200:Action Potentials; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D004285:Dogs; D005260:Female; D008297:Male; D009206:Myocardium / Q000166:cytology; D015221:Potassium Channels / Q000502:physiology*; D011412:Propanolamines / Q000494:pharmacology; D016276:Ventricular Function
chemical_list: D000889:Anti-Arrhythmia Agents; D015221:Potassium Channels; D011412:Propanolamines; C074334:almokalant