Current recordings of noninjected oocytes or oocytes expressing wt hAE1. (A) The representative electric signal of oocytes (noninjected or injected with wt hAE1 cRNA) measured during voltage clamp protocol either in regular MBS or MBS devoid of Na⁺. Na⁺ was substituted by impermeant cation NMDG or by K⁺. (B) Current-voltage curves obtained with control oocytes (noninjected) or oocytes injected with wild-type hAE1 2 days after injection. The current values were taken at 500 ms. The currents were recorded in control medium (MBS, black diamonds) or in MBS where Na⁺ was substituted by NMDG (◊), or by K⁺ (▲). Data presented are means (± SEM) of 20 oocytes coming from different batches.