Effects of 1 mM SITS, an inhibitor of Na+:HCO
-symport, and 20 mM acetate on the pHi regulation of an isolated rat liver perfused with 50 mM ethanol. This concentration was chosen in order to better visualize the effects on pHi. The high acetate concentration added during the initial KHB perfusion crossed the cell membrane only in protonated form (acetic acid) which was immediately dissociated in the cytosol owing to the difference between the actual pHi and its pKa, thus resulting in a pHi decrease (acid load). Conversely, at the beginning of the rinsing phase with KHB, the excess of cytosolic acetate flushed out of the cell as acetic acid form had trapped the cytosolic proton, resulting in a pHi increase.