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Sodium chloride transport across the chicken coprodeum. Basic characteristics and dependence on sodium chloride intake
Author(s) -
Choshniak I.,
Munck B. G.,
Skadhauge E.
Publication year - 1977
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.1977.sp012010
Subject(s) - paracellular transport , sodium , chemistry , chloride , brush border , biophysics , biochemistry , membrane , permeability (electromagnetism) , biology , vesicle , organic chemistry
1. The transport characteristics of the chicken coprodeum have been examined in vitro using the isolated mucosa. The short‐circuit current ( I sc ), the transepithelial electrical potential difference (p.d.), the unidirectional transmural fluxes ( J ms , J sm ) of sodium and chloride measured in the short‐circuited state, and the unidirectional influx of sodium and chloride across the brush border membrane measured under open‐circuit conditions have been studied. The effect of the sodium chloride contents of the diet on these parameters have been investigated. 2. The isolated mucosa depends functionally on the presence of glucose in the incubation media. This dependence reflects the need of glucose as a fuel. There is no indication of coupling between transport of sugars and sodium across the brush border membrane. For preparations from chickens on a low sodium diet a very high and stable I sc can quantitatively be accounted for by the net transport of sodium. Influx of sodium across the brush border membrane is not significantly different from the net flux of sodium. By feeding the chickens a high sodium diet the I sc is reduced by more than 95%, the net transport of sodium is abolished, and the transepithelial electrical conductance is reduced by more than 50%. 3. Both unidirectional transepithelial fluxes of chloride, and the serosa to mucosa flux of sodium appear to proceed through a paracellular shunt. 4. Under the conditions of the low sodium diet the paracellular pathway appears to be anion selective. Whereas, under the conditions of the high sodium regimen the paracellular route appears to be cation selective. After adaptation to a high sodium diet the influx of sodium across the brush border membrane is only moderately reduced. Consequently the decisive event in the adaptation must be localized elsewhere.