Molecular dissection of cardiac repolarization by in vivo Kv4.3 gene transfer
Uta C. Hoppe, … , Eduardo Marbán, David C. Johns
Uta C. Hoppe, … , Eduardo Marbán, David C. Johns
Published April 15, 2000
Citation Information: J Clin Invest. 2000;105(8):1077-1084. https://doi.org/10.1172/JCI8757.
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Molecular dissection of cardiac repolarization by in vivo Kv4.3 gene transfer

Abstract

Heart failure leads to marked suppression of the Ca2+-independent transient outward current (Ito1), but it is not clear whether Ito1 downregulation suffices to explain the concomitant action potential prolongation. To investigate the role of Ito1 in cardiac repolarization while circumventing culture-related action potential alterations, we injected adenovirus vectors in vivo to overexpress or to suppress Ito1 in guinea pigs and rats, respectively. Myocytes were isolated 72 hours after intramyocardial injection and stimulation of the ecdysone-inducible vectors with intraperitoneal injection of an ecdysone analog. Kv4.3-infected guinea pig myocytes exhibited robust transient outward currents. Increasing density of Ito1 progressively depressed the plateau potential in Kv4.3-infected guinea pig myocytes and abbreviated action potential duration (APD). In vivo infection with a dominant-negative Kv4.3-W362F construct suppressed peak Ito1 in rat ventriculocytes, elevated the plateau height, significantly prolonged the APD, and resulted in a prolongation by about 30% of the QT interval in surface electrocardiogram recordings. These results indicate that Ito1 plays a crucial role in setting the plateau potential and overall APD, supporting a causative role for suppression of this current in the electrophysiological alterations of heart failure. The electrocardiographic findings indicate that somatic gene transfer can be used to create gene-specific animal models of the long QT syndrome.

Authors

Uta C. Hoppe, Eduardo Marbán, David C. Johns

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Action potentials of rat cardiomyocytes were prolonged by dominant-negat...
Action potentials of rat cardiomyocytes were prolonged by dominant-negative in vivo Ito1 suppression. Infection of rat myocytes with AdE8I-Kv4.3W362F substantially changed the action potential waveform (c and d) compared with noninfected cells (a and b), resulting in an elevation of the plateau phase and prolongation of the overall APD. In 1 rat myocyte, Ito1 reduction led to a notch-and-dome–shaped action potential waveform (d) and to frequent EADs (e). Mean APDs of wild-type (closed squares; n = 10) and Kv4.3W362F-infected myocytes (closed circles; n = 7) plotted as a function of the percentage of repolarization (f) demonstrate that Ito1 suppression did not exhibit a significant effect on the APD at 10–50% repolarization, but significantly prolonged the APD60 to APD90. Values marked by (A) are significant (P < 0.05).