著者

山口 喬弘 荒船 龍彦 佐久間 一郎 大内 克洋 柴田 仁太郎 本荘 晴朗 神谷 香一郎 児玉 逸雄

出版者

公益社団法人 日本生体医工学会

雑誌

生体医工学 (ISSN:1347443X)

巻号頁・発行日

vol.43, no.1, pp.43-49, 2005

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In heart failure, QT interval and action potential duration (APD) is prolonged and <i>I</i>_Ks, a slow component of delayed rectifier potassium current, decreases. We have reported that the KCNE1 gene, coding <i>I</i>_Ks channel, increases and QT interval is prolonged in patients with heart failure. Since it is known that increasing KCNE1 increases the maximum conductance of the <i>I</i>_Ks channel, the mechanism of APD prolongation is not explained by the over expression of KCNE1. In this study, we construct a cardiac membrane action potential simulation model based on the experimental data from oocytes expression to investigate the relationship between the increase of KCNE1 and APD. In the experiment of oocyte expression, 1 ng and 5 ng of KCNE1 were co-injected with 5 ng of KCNQ1. Expressed currents were recorded 1-2 days after injection by the double-microelectrode voltage clamp method at 35 degrees centigrade. Maximum <i>I</i>_Ks conductance and relationships between time constants, maximum activation parameter and membrane potential were obtained from fitting functions describing <i>I</i>_Ks channel properties in the Luo-Rudy model to experimental results with the Nelder-Mead simplex method. In simulations, APD was prolonged by increasing the co-injected amount of KCNE1. APD at 5 ng KCNE1 was 183 ms, which is 3.4% longer than that at 1 ng KCNE1 (APD=177 ms). This study shows that increasing the KCNE1 expression level makes maximum <i>I</i>_Ks conductance increase and <i>I</i>_Ks channel open slowly and <i>I</i>_Ks conductance decrease according to the APD time scale. Therefore increasing the KCNE1 expression level may prolong APD with this mechanism. This method of constructing a simulation model based on experiments helps to explain the relationship between KCNE1 expression ratio and QT interval prolongation.