Functional characterization of inward rectifier potassium ion channel in murine fetal ventricular cardiomyocytes.
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.
Liu
Aifen
A
Department of Physiology, Tongji Medical College, Huazhong University of Science and Technology, Tongji Medical College, Huazhong University of Science and Technology, China.
Tang
Ming
M
Xi
Jiaoya
J
Gao
Linlin
L
Zheng
Yunjie
Y
Luo
Hongyan
H
Hu
Xinwu
X
Zhao
Fengbo
F
Reppel
Michael
M
Hescheler
Jürgen
J
Liang
Huamin
H
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
C490969:Kcnj4 protein, mouse; C489461:Kir2.1 channel; C489463:Kir2.2 channel; D024661:Potassium Channels, Inwardly Rectifying