title: Functional characterization of inward rectifier potassium ion channel in murine fetal ventricular cardiomyocytes.
abstract: OBJECTIVE
  Previous studies have shown the dramatic changes in electrical properties of murine fetal cardiomyocytes, while details on inward rectifier potassium current (IK1) are still seldom discussed. Thus we aimed to characterize the functional expression and functional role of IK1 in murine fetal ventricular cardiomyocytes.
  
  
  METHODS
  Whole cell patch clamp was applied to investigate the electrophysiological properties of IK1. Quantitative real-time PCR, western blotting and double-label immunofluorescence were further utilized to find out the molecular basis of IK1.
  
  
  RESULTS
  Compared to early developmental stage (EDS), IK1 at late developmental stage (LDS) displayed higher current density, stronger rectifier property and faster activation kinetics. It was paralleled with the downregulation of Kir2.3 and the upregulation of Kir2.1/Kir2.2. IK1 contributed to maintain the maximum diastolic potential (MDP), late repolarization phase (LRP) as well as the action potential duration (APD). However, the contribution to MDP and velocity of LRP did not change significantly with maturation.
  
  
  CONCLUSIONS
  During fetal development, the switch of IK1 subtypes from Kir2.1/Kir2.3 to Kir2.1 resulted in the dramatic changes in IK1 electrophysiological properties.
authors.affiliation: Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology, Tongji Medical College, Huazhong University of Science and Technology, China.
authors.forename: Aifen
authors.initials: A
authors.lastname: Liu
authors.forename: Ming
authors.initials: M
authors.lastname: Tang
authors.forename: Jiaoya
authors.initials: J
authors.lastname: Xi
authors.forename: Linlin
authors.initials: L
authors.lastname: Gao
authors.forename: Yunjie
authors.initials: Y
authors.lastname: Zheng
authors.forename: Hongyan
authors.initials: H
authors.lastname: Luo
authors.forename: Xinwu
authors.initials: X
authors.lastname: Hu
authors.forename: Fengbo
authors.initials: F
authors.lastname: Zhao
authors.forename: Michael
authors.initials: M
authors.lastname: Reppel
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hescheler
authors.forename: Huamin
authors.initials: H
authors.lastname: Liang
mesh_terms: D000818:Animals; D047108:Embryonic Development; D005333:Fetus / Q000166:cytology / Q000378:metabolism; D006352:Heart Ventricles / Q000166:cytology; D007700:Kinetics; D051379:Mice; D032383:Myocytes, Cardiac / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
chemical_list: C490969:Kcnj4 protein, mouse; C489461:Kir2.1 channel; C489463:Kir2.2 channel; D024661:Potassium Channels, Inwardly Rectifying