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Rheogenic sodium transport in a tight epithelium, the amphibian skin.
Author(s) -
Nagel W
Publication year - 1980
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1980.sp013242
Subject(s) - hyperpolarization (physics) , paracellular transport , transcellular , chemistry , biophysics , ouabain , membrane potential , epithelial polarity , toad , sodium , apical membrane , amiloride , intracellular , membrane , conductance , membrane transport , permeability (electromagnetism) , biochemistry , endocrinology , biology , stereochemistry , mathematics , organic chemistry , combinatorics , nuclear magnetic resonance spectroscopy
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.