Effect of external cation and anion substitutions on sodium transport in isolated frog skin

Effects of changes in external ionic strength, external cation and/or anion substitution on transepithelial influx and efflux of sodium, short-circuit current and on transepithelial potential difference and resistance were studied in isolated frog skin. Active transport of Na was found to be highly...

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Bibliographic Details
Published in:The Journal of membrane biology 1980-06, Vol.52 (2), p.121-132
Main Authors: Biber, T U, Mullen, T L
Format: Article
Language:English
Subjects:
Animals
Anura
Biological Transport, Active - drug effects
Bromides - pharmacology
Cesium - pharmacology
Chlorides - pharmacology
Choline - pharmacology
Hydrogen-Ion Concentration
Iodides - pharmacology
Lithium - pharmacology
Membrane Potentials
Osmolar Concentration
Potassium - pharmacology
Rana pipiens
Rubidium - pharmacology
Skin - metabolism
Sodium - metabolism
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Summary:Effects of changes in external ionic strength, external cation and/or anion substitution on transepithelial influx and efflux of sodium, short-circuit current and on transepithelial potential difference and resistance were studied in isolated frog skin. Active transport of Na was found to be highly dependent on both anionic and cationic composition of external medium. Relative abilities of external monovalent cations to inhibit active Na transport were H greater than Li greater than K greater than Rb greater than Cs greater than choline. Relative abilities of external monovalent anions to stimulate active Na transport were I greater than Br greater than Cl. Sequences of anion interaction and of resistance changes suggest that anionic stimulation of Na transport is not due to electrical coupling across outer cell membrane. The ability of different anions and cations to alter Na transport suggests that externally located charged groups act as important barriers or filters to ion movement. In addition, the experiments suggest that an increase in ionic strength of external medium has an effect on active transport of Na, a finding that indicates interference of surface charges with Na entry. Directional changes in efflux of Na due to changes in ionic composition of external medium usually paralleled changes in active Na transport. It is possible that the observed relationship between influx and efflux of Na is the result of common pathways and of interaction of the active transport system with Na efflux.
ISSN:0022-2631
1432-1424
DOI:10.1007/BF01869117