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Unloaded rat hearts in vivo express a hypertrophic phenotype of cardiac repolarization.
J Mol Cell Cardiol. 2008 Nov; 45(5):633-41.JM

Abstract

Cardiac unloading with left ventricular assist devices is increasingly used to treat patients with severe heart failure. Unloading has been shown to improve systolic and diastolic function, but its impact on the repolarization of left ventricular myocytes is not known. Unloaded hearts exhibit similar patterns of gene expression as hearts subjected to an increased hemodynamic load. We therefore hypothesized that cardiac unloading also replicates the alterations in action potential and underlying repolarizing ionic currents found in pressure-overload induced cardiac hypertrophy. Left ventricular unloading was induced by heterotopic heart transplantation in syngenic male Lewis rats. Action potentials and underlying K+ and Ca2+ currents were investigated using whole-cell patch-clamp technique. Real-time RT-PCR was used to quantify mRNA expression of Kv4.2, Kv4.3, and KChIP2. Unloading markedly prolonged cardiac action potentials and suppressed the amplitude of several repolarizing K+ currents, in particular of the transient outward K+ current I(to), in both, epicardial and endocardial myocytes. The reduction of I(to) was associated with significantly lower levels of Kv4.2 and Kv4.3 mRNAs in epicardial myocytes, and of KChIP2 mRNA in endocardial myocytes. Concomitantly, the L-type Ca2+ current was increased in myocytes of unloaded hearts. Collectively, these results show that left ventricular unloading induces a profound remodelling of cardiac repolarization with action potential prolongation, downregulation of repolarizing K+ currents and upregulation of the L-type Ca2+ current. This indicates that unloaded rat hearts in vivo express a hypertrophic phenotype of cardiac repolarization at the cellular and the molecular level.

Authors+Show Affiliations

Institut für Vegetative Physiologie und Pathophysiologie, Universitätsklinikum Hamburg Eppendorf, Germany. schwoere@uke.uni-hamburg.deNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

18721926

Citation

Schwoerer, Alexander Peter, et al. "Unloaded Rat Hearts in Vivo Express a Hypertrophic Phenotype of Cardiac Repolarization." Journal of Molecular and Cellular Cardiology, vol. 45, no. 5, 2008, pp. 633-41.
Schwoerer AP, Melnychenko I, Goltz D, et al. Unloaded rat hearts in vivo express a hypertrophic phenotype of cardiac repolarization. J Mol Cell Cardiol. 2008;45(5):633-41.
Schwoerer, A. P., Melnychenko, I., Goltz, D., Hedinger, N., Broichhausen, I., El-Armouche, A., Eschenhagen, T., Volk, T., & Ehmke, H. (2008). Unloaded rat hearts in vivo express a hypertrophic phenotype of cardiac repolarization. Journal of Molecular and Cellular Cardiology, 45(5), 633-41. https://doi.org/10.1016/j.yjmcc.2008.02.271
Schwoerer AP, et al. Unloaded Rat Hearts in Vivo Express a Hypertrophic Phenotype of Cardiac Repolarization. J Mol Cell Cardiol. 2008;45(5):633-41. PubMed PMID: 18721926.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Unloaded rat hearts in vivo express a hypertrophic phenotype of cardiac repolarization. AU - Schwoerer,Alexander Peter, AU - Melnychenko,Ivan, AU - Goltz,Diane, AU - Hedinger,Nils, AU - Broichhausen,Irene, AU - El-Armouche,Ali, AU - Eschenhagen,Thomas, AU - Volk,Tilmann, AU - Ehmke,Heimo, Y1 - 2008/03/10/ PY - 2007/10/17/received PY - 2008/02/11/revised PY - 2008/02/12/accepted PY - 2008/8/30/pubmed PY - 2009/2/4/medline PY - 2008/8/30/entrez SP - 633 EP - 41 JF - Journal of molecular and cellular cardiology JO - J Mol Cell Cardiol VL - 45 IS - 5 N2 - Cardiac unloading with left ventricular assist devices is increasingly used to treat patients with severe heart failure. Unloading has been shown to improve systolic and diastolic function, but its impact on the repolarization of left ventricular myocytes is not known. Unloaded hearts exhibit similar patterns of gene expression as hearts subjected to an increased hemodynamic load. We therefore hypothesized that cardiac unloading also replicates the alterations in action potential and underlying repolarizing ionic currents found in pressure-overload induced cardiac hypertrophy. Left ventricular unloading was induced by heterotopic heart transplantation in syngenic male Lewis rats. Action potentials and underlying K+ and Ca2+ currents were investigated using whole-cell patch-clamp technique. Real-time RT-PCR was used to quantify mRNA expression of Kv4.2, Kv4.3, and KChIP2. Unloading markedly prolonged cardiac action potentials and suppressed the amplitude of several repolarizing K+ currents, in particular of the transient outward K+ current I(to), in both, epicardial and endocardial myocytes. The reduction of I(to) was associated with significantly lower levels of Kv4.2 and Kv4.3 mRNAs in epicardial myocytes, and of KChIP2 mRNA in endocardial myocytes. Concomitantly, the L-type Ca2+ current was increased in myocytes of unloaded hearts. Collectively, these results show that left ventricular unloading induces a profound remodelling of cardiac repolarization with action potential prolongation, downregulation of repolarizing K+ currents and upregulation of the L-type Ca2+ current. This indicates that unloaded rat hearts in vivo express a hypertrophic phenotype of cardiac repolarization at the cellular and the molecular level. SN - 1095-8584 UR - https://www.unboundmedicine.com/medline/citation/18721926/Unloaded_rat_hearts_in_vivo_express_a_hypertrophic_phenotype_of_cardiac_repolarization_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0022-2828(08)00315-5 DB - PRIME DP - Unbound Medicine ER -