FIGURE 4.

Cation selectivity and inhibition of HIP14- and HIP14L-mediated Mg²⁺ currents expressed in Xenopus oocytes. A, summary of substrate specificity of HIP14 and HIP14L following application of Ca²⁺, 2.0 mm, and other test cations, 0.2 mm, in the absence of external Mg²⁺. Oocytes were clamped at a holding potential of -15 mV and then stepped from -150 to +25 mV in 25-mV increments for 2 s for each of the cations. Values are mean ± S.E. for the permeability ratios measured at the end of each voltage sweep for the respective divalent cation. B, inhibition of Mg²⁺-evoked currents in HIP14-expressing oocytes with 5.0 mm Ca²⁺ or 0.2 mm Co²⁺ in the presence of external 2.0 mm Mg²⁺. Results are mean ± S.E. based on the changes in the E_rev for the respective study. The inhibitor, either CaCl₂ or CoCl₂ was added with MgCl₂ and the voltage clamp was performed about 5 min later.