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Pflügers Archiv

, Volume 411, Issue 5, pp 505–513 | Cite as

Na transport stimulation by novobiocin: intracellular ion concentrations and membrane potential

  • Roger Rick
  • Franz X. Beck
  • Adolf Dörge
  • Edeltraud Sesselmann
  • Klaus Thurau
Transport Processes, Metabolism and Endocrinology; Kidney, Gastrointestinal Tract, and Exocrine Glands

Abstract

Microelectrodes and electron microprobe analysis were employed to study the effect of novobiocin on membrane potential and intracellular electrolyte concentrations in the frog skin epithelium. In both species investigated (Rana esculenta andRana temporaria), novobiocin (1 mM, outer bath) caused a stimulation of transepithelial Na transport, a depolarization of apical membrane potential, a fall in the apical fractional resistance, and an increase in the intracellular Na concentration. The rise in the Na concentration was accompanied by an equivalent fall in the K concentration. All effects of novobiocin were fully reversible by subsequent application of amiloride. The depolarization as well as the Na increase suggests that the natriferic effect of novobiocin is due to a stimulation of the apical Na influx. Combining both measurements it was possible to calculate the effect of novobiocin on the Na permeability of the apical membrane directly. InRana esculenta novobiocin increased the permeability from 4.5 to 23.2 nm/s. InRana temporaria the increase was significantly smaller, from 8.7 to 16.9 nm/s. The transport rate as measured by the short-circuit current showed a non-linear dependence on the apical Na permeability. In the range of transport rates normally encountered, however, the current was a linear function of the Na permeability consistent with the view that the apical membrane is rate-limiting in transepithelial Na transport.

Key words

Novobiocin Amiloride Transepithelial Na transport Intracellular ion concentrations X-ray microanalysis Intracellular microelectrodes Na permeability 

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Copyright information

© Springer-Verlag 1988

Authors and Affiliations

  • Roger Rick
    • 1
  • Franz X. Beck
    • 1
  • Adolf Dörge
    • 1
  • Edeltraud Sesselmann
    • 1
  • Klaus Thurau
    • 1
  1. 1.Physiologisches InstitutUniversität MünchenMünchenGermany

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