The major HCO3- transporter of the renal proximal tubule (PiT), which is situated at the basolateral membrane (BLM), is the electrogenic Na/HCO3 cotransporter (symporter), which also contributes significantly to Na+ reabsorption. Most cells' intracellular pH (pHi) is controlled by HCO3 transporters, which also affects blood pH. The proximal renal tubules from perfused Ambystoma tigrinum (salamander) were used to discover this electrogenic Na/HCO3 cotransporter. This novel cotransporter, which is electrogenic and mediates the movement of one Na+ ion with multiple HCO3- ions, does not rely on intracellular or extracellular Cl- and is blocked by stilbene compounds. This cotransporter as well as others like it have been identified in various tissues and cell types.