Current sensitivity to changes in extracellular ion composition. Oocytes expressing the different hAE1 point mutations (A: L687P, B: D705Y, C: S731P, and D: H734R) were bathed in different media: MBS (Na⁺, K⁺, and Cl⁻-containing medium, ♦), NMDG medium (Na⁺ was substituted by NMDG, ◊), KCl medium (Na⁺ was substituted by K⁺, ▲), and gluconate medium (NaCl and KCl were substituted by NaGluconate and KGluconate, ○). For each mutation, the same batch of 5 oocytes was voltage-clamped in the different media. The data plotted are from one representative experiment; data are means (± SEM) of 5 oocyte measurements. When not seen, the sem was smaller than the symbols.