Inhibition of MagT1-mediated currents. A,inhibition of Mg2+-evoked currents with 0.2 mM test cation in the presence of external 2.0 mM Mg2+. For clarity, only Cu2+, Mn3+, and Zn2+ relative to Mg2+ are represented. Values are mean ± SEM of currents measured at the end of each voltage sweep for the respective cation. B, summary of inhibition by multivalent cations of Mg2+ currents based on the change in Erev represented in Fig. 10A. The inhibitor was added with MgCl2 and voltage-clamp was performed about 5 min later.