Short-term effects of rapid pacing on mRNA level of voltage-dependent K(+) channels in rat atrium: electrical remodeling in paroxysmal atrial tachycardia.
Circulation
; 101(16): 2007-14, 2000 Apr 25.
Article
em En
| MEDLINE
| ID: mdl-10779469
ABSTRACT
BACKGROUND:
Atrial fibrillation causes electrophysiological changes of the atrium, thereby facilitating its maintenance. Although the expression of ion channels is modulated in chronic atrial fibrillation, it is yet unknown whether paroxysmal atrial fibrillation can also lead to electrical remodeling by affecting gene expression. METHODS ANDRESULTS:
To examine the short-term effects of rapid pacing on the mRNA level of voltage-dependent K(+) channels, high-rate atrial pacing was performed in Sprague-Dawley rat hearts. Total RNA was prepared from the atrial appendages from 0 to 8 hours after the onset of pacing, and mRNA levels of Kv1.2, Kv1. 4, Kv1.5, Kv2.1, Kv4.2, Kv4.3, erg, KvLQT1, and minK were determined by RNase protection assay. Among these 9 genes, the mRNA level of the Kv1.5 channel immediately and transiently increased, with bimodal peaks at 0.5 and 2 hours after the onset of pacing. Conversely, the pacing gradually and progressively decreased the mRNA levels of the Kv4.2 and Kv4.3 channels. The increase of Kv1.5 and the decrease of Kv4.2 and Kv4.3 mRNA levels were both rate dependent. In correspondence with the changes in the mRNA level, Kv1. 5 channel protein transiently increased in the membrane fraction of the atrium during a 2- to 8-hour pacing period. Electrophysiological findings that the shortening of the action potential produced by 4-hour pacing was almost abolished by a low concentration of 4-aminopyridine implied that the increased Kv1.5 protein was functioning.CONCLUSIONS:
Even short-term high-rate atrial excitation could differentially alter the mRNA levels of Kv1.5, Kv4.2, and Kv4.3 in a rate-dependent manner. In particular, increased Kv1.5 gene expression, having a transient nature, implied the possible biochemical electrical remodeling unique to paroxysmal tachycardia.
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Base de dados:
MEDLINE
Assunto principal:
Marca-Passo Artificial
/
Taquicardia Atrial Ectópica
/
Canais de Potássio
/
Função Atrial
/
Canais de Potássio de Abertura Dependente da Tensão da Membrana
/
Miocárdio
Idioma:
En
Ano de publicação:
2000
Tipo de documento:
Article