Characterization of bicarbonate-dependent potassium uptake in cultured corneal endothelial cells

N. Savion, N. Farzame, H. B. Berlin

Research output: Contribution to journalArticlepeer-review

Abstract

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. This novel pump made a significant contribution to total K+ influx in BCE cells and may contribute to the fluid pump activity in addition to the well established contribution of the Na+, K+-ATPase pump.

Original languageEnglish
Pages (from-to)690-697
Number of pages8
JournalInvestigative Ophthalmology and Visual Science
Volume30
Issue number4
StatePublished - 1989

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