Figure 5. Na⁺‐dependence of wild‐type and mutant NBCe1‐A activity in oocytes .

A, current–voltage relationships from a representative H₂O‐injected oocyte during sequential exposure to a ‘+Na/0HCO₃ ^’, a +’Na/+HCO₃ ^’ and a ‘0Na/+HCO₃ ^’ solution. Note that the data fell on top of each other and thus the sets have been offset from each other by 3 mV for clarity. Equivalent representative data are shown for oocytes expressing (B) WT‐EGFP, (C) R510H‐EGFP, (D) Q913R‐EGFP and (E) a mixture of R510H‐EGFP and Q913R‐EGFP. F, averaged membrane conductances for each group of cells in each solution, measured between −20 mV and +20 mV, where the outward currents elicited by electrogenic Na/HCO₃ import in our protocol are the largest. ^* P < 0.01 in a paired one‐tailed t test between groups indicated by a horizontal bracket. n.s., no significant difference.