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Regulation of cardiac excitation–contraction coupling by action potential repolarization: role of the transient outward potassium current ( I to )
Author(s) -
Sah Rajan,
Ramirez Rafael J.,
Oudit Gavin Y.,
Gidrewicz Dominica,
Trivieri Maria G.,
Zobel Carsten,
Backx Peter H.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.026468
Subject(s) - repolarization , cardiac transient outward potassium current , excitation–contraction coupling , cardiac action potential , contraction (grammar) , potassium channel , ventricular action potential , potassium , transient (computer programming) , chemistry , medicine , cardiology , biophysics , electrophysiology , myocyte , patch clamp , biology , computer science , organic chemistry , operating system
The cardiac action potential (AP) is critical for initiating and coordinating myocyte contraction. In particular, the early repolarization period of the AP (phase 1) strongly influences the time course and magnitude of the whole‐cell intracellular Ca 2+ transient by modulating trans‐sarcolemmal Ca 2+ influx through L‐type Ca 2+ channels ( I Ca,L ) and Na‐Ca exchangers ( I Ca,NCX ). The transient outward potassium current ( I to ) has kinetic properties that make it especially effective in modulating the trajectory of phase 1 repolarization and thereby cardiac excitation‐contraction coupling (ECC). The magnitude of I to varies greatly during cardiac development, between different regions of the heart, and is invariably reduced as a result of heart disease, leading to corresponding variations in ECC. In this article, we review evidence supporting a modulatory role of I to in ECC through its influence on I Ca,L , and possibly I Ca,NCX . We also discuss differential effects of I to on ECC between different species, between different regions of the heart and in heart disease.