Fig. 2.

[H⁺_o] and [Gua⁺_o] dependence of uncoupled currents through Na/K pumps. (A) I–V relationships of ouabain-sensitive currents in the absence of Na⁺_o and K⁺_o in solutions containing 120 mM NMG⁺_o (squares) or 120 mM Gua⁺_o (diamonds) at pH 7.6 (black), pH 6.6 (gray), or pH 8.6 (open symbols). (Inset) The visually estimated by the B-spline line connecting the average data (V_rev) as a function of pH_o in each external solution. (B) I–V curves (pH_o 8.6) with varying [Gua⁺_o]. (Inset) V_rev (estimated as in A) as a function of [Gua⁺_o]. Data points are means ± SEM of 5 to 15 experiments in each condition. Currents were normalized to the current induced by 10 mM K⁺_o in NMG⁺_o at 0 mV.