Sabine Faber

Intracellular pH Regulation in Bovine Aortic Endothelial Cells: Evidence of Both Na+/H+ Exchange and Na+-Dependent Cl–/HCO–3 Exchange

Regulation of intracellular pH (pH_i) was studied in cultured bovine aortic endothelial cells, an important cell system for cardiovascular research. Suspended cells were acidified by the NH₄Cl prepulse technique as well as by exposure to CO₂/HCO^–₃. Subsequent rates of pH_i recovery were monitored using the fluorescent dye 2′,7′-bis(2-carboxyethyl)-5-(6)-carboxyfluorescein (BCECF). In HCO^–₃-free solutions, an EIPA-sensitive, Na⁺-dependent mechanism fully accounted for realkalinization, namely the Na⁺/H⁺ exchanger (NHE). In the presence of HCO^–₃, an additional acid efflux mechanism was found. This one was dependent on Na⁺ and intracellular Cl^–, EIPA-insensitive but DIDS-sensitive, and therefore represented a Na⁺-dependent Cl^–/HCO^–₃ exchanger (NCBE). In summary, two acid-extruding mechanisms were identified in bovine aortic endothelial cells: NHE and NCBE.

A Novel Screening Assay of the Na+-Dependent Cl-/HCO-3 Exchanger (NCBE) and Its Inhibitors

A mouse fibroblast L cell line defective in Na+/H+ antiport activity (LAP1) was used to develop a screening assay for the Na+-dependent Cl-/HCO–3