Figure 3. Oleoyl-CoA reduce the ATP sensitivity by an electrostatic mechanism.

A, effects of 20 μM oleoyl-CoA, 2 μg ml⁻¹ polylysine and ATP on cardiac K_ATP channels. B, from the experiment in A, concentration-response curves for ATP inhibition were obtained before oleoyl-CoA (1), after oleoyl-CoA (2) and after polylysine (3). C, effects of Mg²⁺ in the presence and absence of 1 mM ATP on K_ATP channels subsequent to the application of 20 μM oleoyl-CoA. D, the amount of ATP inhibition was used to estimate the K_i(ATP) using the Hill equation for ATP inhibition (Fig. 1C) with a Hill coefficient of 1.8. A plot of these K_i(ATP) values against the respective Mg²⁺ concentrations resulted in a concentration-response curve that was fitted to a standard Hill function with an IC_50(Mg2+) of 1.3 ± 0.2 mM and Hill coefficient of 1. E, effects of Mg²⁺ in the presence and absence of 1 mM ATP on K_ATP channels subsequent to the application of 20 μM PIP₂. The amount of ATP inhibition was used to estimate the K_i(ATP) using the Hill equation for ATP inhibition (Fig. 1C) with a Hill coefficient of 1.8. A plot of these K_i(ATP) values against the respective Mg²⁺ concentrations resulted in a concentration-response curve that was fitted to a standard Hill function with an IC_50(Mg2+) of 1.5 ± 0.2 mM and Hill coefficient of 1.