Figure 6. Summary of pH_i recovery rates (dpH_i/dt) of oocytes expressing human NBCn1 EGFP-tagged constructs (A), untagged constructs (B) or various NBCn1-G constructs (C).

The full-length cDNAs encoding human NBCn1-B and -D have yet to be cloned. Thus, we artificially generated them based on the known rat and mouse full-length clones. D.1 represents the minor variant of NBCn1-D that contains the ‘VTSR’ extension in the MEAD module. All human NBCn1 variants in A were tagged with EGFP at the Ct. NBCn1-B and -H in B and NBCn1-G in C contain no EGFP tag. The NBCn1-G-ΔIII in C was created by introducing a stop codon immediately after the ‘VKALK’ motif before cassette III, on the background of human NBCn1-G. Oocytes were superfused in a protocol like that in Fig. 5. dpH_i/dt represents the pH_i recovery rate during the first CO₂/HCO₃⁻ exposure, analogous to the slope of the dashed line in Fig. 5. For all groups of NBCn1 variants or the truncated NBCn1 construct, the dpH_i/dt values are significantly different from that of the control H₂O-injected oocytes, based on a one-way ANOVA followed by Dunnett's multiple comparison. Bars for control H₂O in B and C are reproduced from A. An asterisk indicates groups significantly different by one-way ANOVA followed by post hoc Tukey's comparison. Numbers in parenthesis: N of oocytes.