Inward-directed current generated by the Na+,K+ pump in Na+- and K+-free medium
Article first published online: 2 JAN 2013
© The Author(s) Journal compilation © 1993 International Federation for Cell Biology
Cell Biology International
Volume 17, Issue 12, pages 1107–1116, December 1993
How to Cite
Efthymiadis, A., Rettinger, J. and Schwarz, W. (1993), Inward-directed current generated by the Na+,K+ pump in Na+- and K+-free medium. Cell Biology International, 17: 1107–1116. doi: 10.1006/cbir.1993.1043
- Issue published online: 2 JAN 2013
- Article first published online: 2 JAN 2013
- Paper received 11.10.93. Paper accepted 26.11.93.
- Cited By
In Na+- and K+-free solution, an inward-directed current can be detected in Xenopus oocytes, which is inhibited by cardic glycosides and activated by ATP. Therefore, it is assumed to be generated by the Na+, K+ pump. At negative membrane potentials, the pump current increases with more negative potentials and with increasing [H+] in the external medium. This current is not observed when Mg2+ instead of Ba2+ is the only divalent cation present in the bath medium, and it does not depend on whether Na+ or K+ is present internally. At 5 to 10 mM Na+ externally, maximum pump-generated current is obtained while no current can be detected in presence of physiological [Na+]. It is suggested that in low-Na+ and K+-free medium the Na+, K+ pump molecule can either form a conductive pathway that is permeable to Ba2+ or protons or operate in its conventional transport mode accepting Ba2+ as a K+ congener. A reversed pump mode or an electrogenic uncoupled Na+-efflux mode is excluded.