Clofilium-induced Block of Delayed Rectifier Type K+Current in Atrial Tumor Cells (AT-1 Cells)

Clofilium-induced Block of Delayed Rectifier Type K+Current in Atrial Tumor Cells (AT-1 Cells).Journal of Molecular and Cellular Cardiology(1997)29, 301–307. Atrial tumor myocytes derived from transgenic mice (AT-1 cells) have been shown to express mRNAs encoding cardiac K+channels and display a cardiac electrophysiological phenotype. The major K+current is the rapid component of the delayed rectifier (Ikr). The purpose of the study was to characterize the mode of action of a class III anti-arrhythmic agent (C3A), clofilium, in these cells to elucidate further the mechanism and functional consequence of block. We show that clofilium blocks this Ikrin a dose-dependent manner with IC50of 1.25μ . Clofilium induced block was irreversible for higher concentrations (≥50μ ) and partially reversible for lower doses. The reversal potential for this current was −77.5±1.5 mV. The block is voltage dependent and the drug probably binds the channel in the open state.