Characterization of bicarbonate-dependent potassium uptake in cultured corneal endothelial cells.
Bovine corneal endothelial (BCE) cells in culture demonstrated 86Rb+ uptake which was mostly ouabain-sensitive with some (15 to 50%) ouabain-insensitive uptake that was dependent on the presence of bicarbonate in the incubation medium. Bovine smooth muscle (SM) cells demonstrated ouabain-sensitive 86Rb+ uptake but the ouabain-insensitive 86Rb+ uptake was not bicarbonate-dependent. Although omission of bicarbonate from the incubation buffer resulted in some reduction in the pH, this change was not responsible for the reduction in the ouabain-insensitive 86Rb+ uptake. Furthermore, the removal of bicarbonate decreased the 86Rb+ influx but not its efflux. This ouabain-insensitive and bicarbonate-dependent 86Rb+ influx in BCE cells proceeded at a linear rate for at least 60 min and increased as a function of bicarbonate concentration such that almost maximal uptake was observed at a concentration of about 10 to 15 mM. Saturation of the bicarbonate-dependent 86Rb+ pump in BCE cells occurred at a concentration of 2 mM Rb+ in the incubation buffer, similar to the previously observed value for the Na+, K+-ATPase. Competition experiments with both unlabeled Rb+ and K+ demonstrated that likewise in the Na+, K+-ATPase the 86Rb+ influx represented physiological influx of K+. Furthermore, the energy requirements of the bicarbonate-dependent 86Rb+ uptake were similar to those of the 86Rb+ uptake via the Na+, K+-ATPase. The results described in this work demonstrated a novel bicarbonate-dependent K+ pump in addition to the Na+, K+-ATPase pump.(ABSTRACT TRUNCATED AT 250 WORDS)
Savion
N
N
Maurice and Gabriela Goldschleger Eye Research Institute, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Hashomer, Israel.
Farzame
N
N
Berlin
H B
HB
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002417:Cattle; D002478:Cells, Cultured; D004728:Endothelium, Corneal / Q000166:cytology / Q000378:metabolism*; D004734:Energy Metabolism; D009130:Muscle, Smooth / Q000166:cytology / Q000378:metabolism; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012413:Rubidium / Q000378:metabolism; D012414:Rubidium Radioisotopes
D001639:Bicarbonates; D012414:Rubidium Radioisotopes; D010042:Ouabain; D012413:Rubidium; D011188:Potassium