Characterization of Mg2+-evoked currents in Xenopus oocytes expressing hMagT1. A, effect of pH on Mg2+-evoked currents. Currents were measured in standard solutions containing 2.0 mM MgCl2 at the pH values indicated. B, summary of mean currents with external pH at a holding potential of -125 mV. Mg2+ did not evoke currents in H2O-injected oocytes at any of the pH values tested.