Figure 6.

Mg²⁺ dose response of hERG and KCNE1-KCNQ1 in the presence of PIP₂ (A) hERG maximal current of a representative cell. hERG maximal current was evaluated from the peak tail current of a 1-s step at 30 mV followed by repolarization at –100 mV repeated every 3 s. PIP₂ was continuously applied. Various concentrations of Mg²⁺ were added as indicated. (B) KCNE1-KCNQ1 maximal current of a representative cell. KCNE1-KCNQ1 maximal current was evaluated from the current at the end of a 1.5-s step at +40 mV followed by repolarization at –60 mV repeated every 3.5 s. Various concentrations of Mg²⁺ were added as indicated. (C) Mg²⁺ dose response data from hERG (N = 10 cells) and KCNE1-KCNQ1 (N = 8 cells). Hill fits are presented for hERG (solid line) and KCNE1-KCNQ1 (dashed line). (D) Deactivation time constants obtained from a monoexponential fit of the deactivating tail current before (control) and after 6 mM Mg²⁺ application in hERG (N = 10 cells) and KCNE1-KCNQ1 (N = 8 cells). ^∗∗p < 0.01.