Fig. 2.

Schematic overview of the proposed transport mechanisms of SCFAs in colonocytes. Across the apical membrane the major part of SCFAs is transported in the dissociated form by an HCO₃⁻ exchanger of unknown identity (?) or by one of the known symporters, MCT1 or SMCT1. A small part may be transported via passive diffusion (spiral). The part of SCFAs that is not oxidized by the colonocytes is transported across the basolateral membrane. The basolateral transport can be mediated by an unknown HCO₃⁻ exchanger, MCT4, or MCT5.