Abstract
Intracellular potentials were measured in beetroot tissue during the steady-state uptake of K+ from various solutions. In solutions containing bicarbonate, the membrane potential becomes up to 70 mv more negative than the estimated equilibrium potential for K+. The uptake of K+ from such solutions is correlated with variations in the potential, both when the bicarbonate concentration is changed and also when the metabolic activity of the tissue is changed by washing in water for various periods. However, the estimated permeability to K+ varies from 0.4 x 10-7 to 1.5 x 10-7 cm·sec-1. It is postulated that the change of potential arises from the metabolic transport of HCO3 - into the cell or H+ outwards, and that the associated uptake of K+ is partly or entirely by passive diffusion across the cell membrane. In contrast, K+ uptake from KCl solutions is not accompanied by any significant change in the membrane potential, which remains relatively close to the K+ equilibrium potential. In solutions containing both KHCO3 and KCl, it appears that an amount of K+ equal to the influx of Cl- is taken up independently of the potential, while the component of K+ uptake which is not balanced by Cl- uptake is related to the potential in the manner described. These results suggest that K+ uptake is linked to Cl- uptake in an electrically neutral active transport process.
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Selected References
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- DIAMOND J. M. The mechanism of solute transport by the gall-bladder. J Physiol. 1962 May;161:474–502. doi: 10.1113/jphysiol.1962.sp006899. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ETHERTON B., HIGINBOTHAM N. Transmembrane potential measurements of cells of higher plants as related to salt uptake. Science. 1960 Feb 12;131(3398):409–410. doi: 10.1126/science.131.3398.409. [DOI] [PubMed] [Google Scholar]
- Etherton B. Relationship of Cell Transmembrane Electropotential to Potassium and Sodium Accumulation Ratios in Oat and Pea Seedlings. Plant Physiol. 1963 Sep;38(5):581–585. doi: 10.1104/pp.38.5.581. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., KATZ B. The effect of sodium ions on the electrical activity of giant axon of the squid. J Physiol. 1949 Mar 1;108(1):37–77. doi: 10.1113/jphysiol.1949.sp004310. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Laties G. G., Macdonald I. R., Dainty J. Influence of the Counter-ion on the Absorption Isotherm for Chloride at Low Temperature. Plant Physiol. 1964 Mar;39(2):254–262. doi: 10.1104/pp.39.2.254. [DOI] [PMC free article] [PubMed] [Google Scholar]