Figure 3. Effects of the maximum conductance and Ca²⁺ affinity of I _SK .

A, stability boundaries plotted for three g _sk, with values of 0, 2.0 and 4.0 μS μF⁻¹. B, stability boundaries plotted for three EC₅₀ values of 1.0, 0.5 and 0.1 μm corresponding to the black, red and green curves, respectively. C, the slope of ΔAPD vs. Δ[Ca²⁺]_peak indicates the ${\mathrm{Ca}}_{\mathrm{i}}^{2+}$→V _m coupling. When g _sk = 0 μS μF⁻¹, the ${\mathrm{Ca}}_{\mathrm{i}}^{2+}$→V _m coupling is positive, while when g _sk = 4.0 μS μF⁻¹, the ${\mathrm{Ca}}_{\mathrm{i}}^{2+}$→V _m coupling is negative. EC₅₀ is 0.7 μm. D, slope (ΔAPD/Δ[Ca²⁺]_peak) vs. g _sk. E, ΔAPD vs. Δ[Ca²⁺]_peak when EC₅₀ is varied. g _sk is 4.0 μS μF⁻¹. F, slope (ΔAPD/Δ[Ca²⁺]_peak) vs. EC₅₀.