The Journal of Membrane Biology

, Volume 61, Issue 2, pp 127–134 | Cite as

Intracellular ionic activities in frog skin

  • W. Nagel
  • J. F. Garcia-Diaz
  • W. McD Armstrong


Intracellular Na+, K+, and Cl activities (a Na i ,a K i ,a Cl i ) and transapical membrane potentials (Vo) were measured with liquid ion-exchanger and open-tip microelectrodes in isolated short-circuited frog skins (R. pipiens) incubated at 23°C in normal amphibian Ringer's solution. Under control conditionsa Na i =14±3mm,a K i =132±10mm anda Cl i =18±3mm (sd). The value ofa Cl i is 4.4 times the value corresponding to electrochemical equilibrium for this ion. Thus, Cl is actively accumulated by epithelial cells of the frog skin. Shortly after addition of amiloride (2–5 μm) to the apical bathing medium,a K i ,a Na i , anda Cl i were essentially unchanged althoughV o had hyperpolarized by about 30–40 mV. During long-term exposure to amiloridea K i anda Cl i did not change significantly,V o depolarized by about 16 mV from the maximal value anda Na i decreased to 8±3mm. Immediately after exposure to amiloride the transmembrane driving force for Na+ increased from 124 to 154 mV. During further exposure to amiloride, despite changes in bothV o anda Na i , this driving force remained virtually constant. SinceIsc during this period was close to zero, it is suggested that the observed driving force for Na+ under these conditions approximates the maximal driving force generated by the Na+−K+ ATP-ase pump in the basolateral cell membrane.

Key words

Frog skin microelectrodes membrane potentials intracellular activities amiloride 


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Copyright information

© Springer-Verlag New York Inc. 1981

Authors and Affiliations

  • W. Nagel
    • 1
  • J. F. Garcia-Diaz
    • 1
  • W. McD Armstrong
    • 1
  1. 1.Department of PhysiologyIndiana University School of MedicineIndianapolis

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