Simulations of hemichannel gating and voltage-dependent ATP efflux. (A and B) Transient integral conductance (middle panels) mediated by Px1 hemichannels (A) and Cx hemichannels (B) stimulated by the depolarizing voltage pulse from V_h to V (top panel) for T seconds. The Px1 conductance was calculated in an arbitrary unit (AU) with Eqs. 7 and 9 at V = 10 mV, V_h = −70 mV, V_g = 50 mV, V_g0 =13 mV, and τ_a = τ_d = τ_i/50 = T/250. The Cx conductance was calculated with Eqs. 8 and 9 at V = 10 mV, V_h = −70 mV, V_g = 50 mV, V_g0 = 13 mV, and τ_d = τ_a/10 =T/50. The related transient ATP efflux (bottom panels) was calculated by using Eqs. 7–9 and Eq. 6 with L = 1, z = 2, i.e., at V₀ = 13 mV, r = 0. (C and D) Normalized quantity of ATP released via Px1 hemichannels versus membrane voltage calculated using Eqs. 11–13 at τ_a = τ_d = τ_i/50 and with T = 50τ_i (C) and T = 5τ_i (D). (E and F) Normalized quantity of ATP released via Cx hemichannels versus membrane voltage calculated using Eqs. 11, 12, and 14 at τ_d = τ_a/10 and with T = 50τ_a (E) and T = 5τ_a (F). The details are in the text.