Sodium bicarbonate cotransporters (NBCs) mediate the coupled movement of sodium and bicarbonate ions across the plasma membrane of many cells. This is an electrogenic process with an apparent stoichiometry of 3 bicarbonate ions per sodium ion. NBC1 has been identified as a key player for regulation of intracellular pH in several cell types. NBC1 Isoform 2 is specifically expressed in kidney at the level of proximal tubules.