Figure 1

Schema for the metabolism of citrate in a proximal tubule cell. The carrier NADC-1 of apical membrane reabsorbs the bivalent citrate. In conditions of acidosis the presence of H⁺ in the proximal tubule fluid stimulates the formation of citrate bivalent from trivalent. The divalent citrate is reabsorbed and metabolized by citrate lyase or through the tricarboxylic acid cycle in the mitochondria of proximal tubular cells. NADC-1 (slc13a2) = Na-dependent low affinity carrier of dicarboxylic acids. NADC-3 (slc13a3) = Na-dependent high affinity carrier of dicarboxylic acids.