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Transport of potassium by the colon of normal and sodium‐depleted rats
Author(s) -
Edmonds C. J.
Publication year - 1967
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.1967.sp008381
Subject(s) - potassium , chemistry , sodium , efflux , flux (metallurgy) , ussing chamber , diffusion , biophysics , choline chloride , analytical chemistry (journal) , endocrinology , medicine , chromatography , secretion , biochemistry , biology , thermodynamics , physics , organic chemistry
1. Ascending and descending segments of colon of normal and Nadepleted rats were perfused with solutions of differing KCl concentration. Net K flux, electrical p.d. and, in some experiments, unidirectional K fluxes were measured. 2. Variation of luminal K concentration over the range 0‐40 m M did not affect p.d. or K efflux rate. 3. K secretion rate fell about 30% when Na‐free choline chloride solution was perfused. 4. Net flux was a linear function of the luminal K concentration, and fell as the latter increased. Na depletion increased K secretion rate and passive permeability of the mucosa to K. Adrenalectomy had the reverse effect. The luminal K concentration, associated with zero net K flux was much greater than expected if the colonic mucosa behaved passively with respect to K. 5. Unidirectional fluxes determined when 5 m M ‐KCl was in the lumen showed that the ratio influx/efflux was much less than predicted by Ussing's flux ratio equation. 6. It was concluded that K influx was due to simple diffusion and K efflux to diffusion and active transport, both processes being increased by Na depletion.