LQT1 rabbits were treated with NS1643 (1.5 mg/kg/min) or vehicle (50% polyethylene glycol 400/50% isotonic glucose 5%) for 45 minutes.

Transfected hEK cells were used for activity evaluation by whole-cell voltage-clamp methods. The coverslips were placed in a 2 cc chamber, which was superfused at a rate of 2 mL/min at room temperature. The pipette solution contained KCl 10 mM, K-aspartate 110 mM, MgCl2 5 mM, Na2 ATP 5 mM, EGTA 10 mM, HEPES 5 mM, and CaCl2 1 mM, corrected to pH 7.2 with KOH. The extracellular solution contained NaCl 140 mM, KCl 5.4 mM, CaCl2 1 mM, MgCl2 1 mM, HEPES 5 mM, and glucose 5.5 mM, corrected to pH 7.4 with NaOH. For IKr measurements, the whole cell configuration of the patch-clamp method was used. The series resistance measured in the solution was <7 MU. Data were sampled at 1 kHz. The holding potential was -80 mV. All tail currents reported in this article represent dofetilide-sensitive currents. The NS1643 (Tocris Bioscience, Ellisville, MO) was dissolved in DMSO (30 mM) first and then diluted into the extracellular solution. All the experiments were performed at room temperature. The data was sampled at 2 kHz and analyzed with the software CLAMPFIT (Axon Instruments, Molecular Devices, Eugene, OR).