hERG potassium channel assay.

To determine the in vitro test article effects on cardiac ion channel current (IKr), the rapidly activating, delayed rectifier potassium current was studied using Chinese hamster ovary (CHO) cells stably expressing the hERG channel encoded by human ether-à-go-go-related gene. Briefly, channel activity was functionally assessed using a high-throughput planar voltage-clamp technology (PatchXpress 7000A). Signal amplitudes were quantified at steady state during control (vehicle) treatment and in the presence of (i) a fixed concentration or (ii) increasing concentrations of the test article. Concentration-dependent changes of signal in response to the test article were expressed as percent block relative to control (predrug/−trigger) and are reported as the means ± standard errors of the means (SEM) of the indicated number of tested cells per wells. IC₅₀s were determined where applicable by fitting the averaged concentration-response data (means ± SEM) with a Hill equation (12).