THE APICAL CL HCO3 EXCHANGER OF BETA-INTERCALATED CELLS/

There are two types of intercalated cells of the renal collecting duct ; one secretes H+ and the other secretes HCO3-. The H+-secreting form has an apical vacuolar H+-ATPase and a basolateral Cl/HCO3 exchanger t hat cross-reacts with antibodies to band 3, the product of the AE1 gen e. The HCO3--secreting form has a basolateral vacuolar H+-ATPase and a n apical Cl/HCO3 exchanger, whose identity has not been established pr eviously. Apical membrane vesicles of beta intercalated cells purified from rabbit kidney cortex contain both an electroneutral Cl/HCO3 exch ange activity and polypeptides that react with antibodies to band 3 on Western blots. Furthermore, both primary cultures of HCO3--secreting intercalated cells and an immortalized cell line derived from these ce lls express AE1 and have an apical Cl/HCO3 exchanger. Apical membranes purified from these cells contain a 100-kDa polypeptide that cross-re acts with antibody to the cytoplasmic domain of band 3. These data sug gest that the apical Cl/HCO3 exchanger of HCO3--secreting intercalated cells is band 3.