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Updated: Aug 8, 2026

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Published on: November 25, 2015
Rheogenic sodium transport in a tight epithelium, the amphibian skin
Abstract:
1. Intracellular potentials from frog and toad skins were measured to identify rheogenic components of active Na transport across the basolateral membrane. Transcellular current flow and associated R . I-drops were blocked with amiloride or Na-free mucosal solution. 2. The potential difference across the basolateral membrane was found to be hyperpolarized by 18 . 5 +/- 1 . 6 mV above the steady-state value immediately after blockage of apical membrane Na conductance. The hyperpolarization disappeared within 15--25 min. 3. The final steady-state value of 93 . 1 +/- 2 . 5 mV was slightly less than reasonable estimates of the K equilibrium potential. 4. The hyperpolarization could not be observed 3--5 min after addition of ouabain (10(-4) M). 5. Both the magnitude and duration of the hyperpolarization correlate directly with the amount of Na accumulated in the intracellular space. 6. A fraction of the intracellular potential was missing when Na transport was re-established after long term blockage of apical membrane Na entry. It reappeared within 10--20 min. 7. It is suggested that the hyperpolarization is due to rheogenic Na transport across the basolateral membranes. This transport mechanism may contribute some 30--50% of the electrical gradient for passive Na entry across the mucosal membrane. 8. A coupling ratio between pumped fluxes of Na and K of about 2:1 is calculated from the data.
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