The electroneutral Na-coupled HCO3- transporter NBCn2, encoded by SLC4A10, plays critical roles in intracellular pH regulation and transepithelial HCO3- movement. In human, dysfunction of SLC4A10 is associated with multiple pathological conditions, including complex epilepsy, mental retardation, autism spectrum disorders, as well as dysmorphic features. We have previously demonstrated that Slc4a10, under the control of two distinct promoters, is capable of expressing two groups of NBCn2 variants differing in the extreme amino termini (Nt), one starting with “MEIK” (the first four residues of the Nt), and the other, “MCDL”. In rat, MEIK-NBCn2 is specifically expressed in the central nervous system, whereas MCDL-NBCn2 is predominantly expressed in the kidney. In the present study, by 5′-rapid amplification of cDNA ends and cDNA cloning, we identified from rat kidney a third new promoter located between the two previous ones in Slc4a10. From this new promoter, two types of Slc4a10 transcripts can be produced, one encoding a protein identical to the previous MCDL-NBCn2. The other lacks exon 3, thus could in theory produce a new type of NBCn2 with a truncation at the Nt. The genomic sequences of the three promoters, including P1 expressing MEIK-NBCn2, the new P2 expressing MCDL- plus the Nt-truncated-NBCn2, and P3 expressing MCDL-NBCn2, were cloned and analyzed by luciferase reporter assay. Among the three promoters, P2 showed the highest activity in human embryonic kidney cells HEK293, while P3 showed just basal activity. Our data are consistent with the notion that MCDL-NBCn2 is expressed under the control of promoter P2 in the kidney. By immunocytochemistry with anti-MCDL-NBCn2, NBCn2 was predominantly localized in the cortex of rat kidney. Surprisingly, a higher magnification view showed that NBCn2 was localized at the apical membrane of epithelial cells in renal tubules, likely the proximal segments. The physiological role of NBCn2 in the kidney remains to be addressed. Our study is important for the field of acid-base transport. Firstly, disclosing the promoters of Slc4a10 represents a critical step forward towards understanding the mechanism underlying the regulation of tissue-specific expression of Slc4a10. Secondly, the characterization of the promoters could also be important for studying the differential regulation of Slc4a10 expression in response to acid-base stress in different tissues. Finally, our finding about the cellular localization of NBCn2 in the kidney might impact our understanding of the molecular mechanism involved in the acid-base transport in renal tubules.