Rats treated with
DOCA salts and subjected to abdominal
aortic stenosis display left ventricle
hypertrophy associated with a decrease in cardiac I(to) current density and prolongation of the action potential duration. We investigated the molecular basis of these electrophysiological defects by analyzing the amount of
mRNA corresponding to the genes encoding the a subunits of the left ventricle K+ channel at the steady state. The mRNAs corresponding to the a subunits of the K+ channel (Kv1.2, Kv1.4, Kv1.5, Kv2. 1, Kv4.2 and Kv4.3) were measured by quantitative RT-PCR using a specific Kv internal standard. In control rats, the Kvl.5 gene was only expressed at a low level, whereas the Kv4.2 and Kv4.3 genes were expressed at a high level. Regardless of the etiology of the
hypertrophy, the amounts of Kv1.4 and Kv1.5 mRNAwere similar in treated,
sham and control rats. The amounts of Kv1.2 and Kv2.1
mRNA were markedly lower in
DOCA-
salt treated rats (66%) than in
sham-
DOCA rats, but no effect was observed after
stenosis. The very conservative Kv4.2 and Kv4.3 genes were found to be downregulated simultaneously in both type of
hypertrophy. However, the steady-state amount of Kv4
mRNA was even lower in rats with
DOCA-
salt-induced
hypertrophy than in those with
stenosis-induced ventricular
hypertrophy. Therefore, the decrease in I(to) density, consecutively to pressure- and volume-overload, is due to a large decrease in the amount of Kv4.2 and Kv4.3
mRNA. In addition,
DOCA-
salt treatment alters the amounts of Kv transcripts independently to
cardiac hypertrophy, suggesting that the
mineralocorticoid may be involved in Kv gene expression.