L-type Calcium Current (ICa,L) and Inward Rectifier Potassium Current (IK1) are Involved in QT Prolongation Induced by Arsenic Trioxide in Rat

The present study was designed to study the effects of As2O3 on QT interval prolongation and to explore the potential ionic mechanisms in isolated rat ventricular cardiomyocytes. The rats of As2O3 group were treated with 0.8 mg.kg(-1.)d(-1) As2O3 intravenously for 7 days consecutively and the control group with saline. The ECG was recorded to calculate heart rate-corrected QT interval (QTc). Single cardiomyocytes were isolated by using collagenase II, and the action potential duration (APD) and ion currents were recorded by whole-cell patch clamp. [Ca2+](i) was examined by confocal laser scanning microscopy. Our data showed that both QTc and APD were prolonged significantly after As2O3 treatment. Meanwhile, As2O3 suppressed I-K1 and shifted the reversal potential to more positive direction. Moreover, the density of I-Ca,I-L was augmented significantly, and the steady-state activation curve became more negative, whereas, the inactivation and reactivation of I-Ca,I-L were not changed notably after As2O3 administration. Furthermore, the maximal [Ca2+](i) was enhanced obviously by either KCl or caffeine stimulation in As2O3 -treated cardiomyocytes. Our results show that the potential mechanism of As2O3-induced QT interval prolongation in rat might be relative to disturbing the fine balance of transmembrane currents (increasing I-Ca,I-L and decreasing I-K1) and causing APD prolongation. Copyright (C) 2010 S. Karger AG, Basel