Figure 2. Ca²⁺ block of I_K(IR) is reversible.

A, inward rectifier current traces of a HCEC bathed in standard bath solution. The cell was held at −60 mV and step potentials were applied from −120 to +20 mV, in 20 mV steps. B, the same cell after superfusion with standard bath solution containing 9 mm Ca²⁺. C, addition of 50 μm Ba²⁺ blocked the remaining current. D, current traces taken after washout of high external Ca²⁺ and Ba²⁺ with standard bath solution. E, current-voltage plots for control, 9 mm Ca²⁺, 50 μm Ba²⁺ and after washout.