Expression of Na+/HCO3- cotransporter and its role in pH regulation in mouse parotid acinar cells.

Ion transporters such as Na+/H+ exchanger (NHE), Cl−/HCO3− exchanger (AE), and Na+/HCO3− cotransporter (NBC) are known to contribute to the intracellular pH (pHi) regulation during agonist-induced stimulation. This study examined the mechanisms for the pHi regulation in the mouse parotid and sublingual acinar cells using the fluorescent pH-sensitive probe, BCECF. The pHi recovery from agonist-induced acidification in the sublingual acinar cells was completely blocked by EIPA, a NHE inhibitor. However, the parotid acinar cells required DIDS, a NBC1 inhibitor, in addition to EIPA in order to block the pHi recovery. Moreover, RT-PCR analysis detected the expression of pancreatic NBC1 (pNBC1) only in the parotid acinar cells. These results provide strong evidence that the mechanisms for the pHi regulation are different in the two types of acinar cells, and pNBC1 contributes to pHi regulation in the parotid acinar cells, whereas NHE is likely to be the exclusive pHi regulator in the sublingual acinar cells.