Figure 16.

Molecular action of electrogenic NCBTs. Possible molecular mechanisms by which an electrogenic NCBT could operate with an apparent Na⁺:HCO₃⁻ stoichiometry of 1:2 (A–D in top panel) and 1:3 (E–J in bottom panel). Note that we have not considered any models that are based on CO₃²⁻-HCO₃⁻ exchange (considered for NBCn1 in FIGURE 30), or models of HCO₃⁻-stimulated electrogenic Na-2H exchange. We have also omitted mechanisms of 1:3 stoichiometry that could result from modification of model D.