Mechanisms of Anion and Cation Permeations in the Resting Membrane of a Barnacle Muscle Fiber |
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| Authors: | S Hagiwara K Toyama and H Hayashi |
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| Institution: | From the Department of Physiology, University of California at Los Angeles Medical School, Los Angeles, California 90024, and the Marine Neurobiology Facility, Scripps Institution of Oceanography, University of California at San Diego, La Jolla, California 92037 |
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| Abstract: | The resting membrane of a barnacle muscle fiber is mostly permeable to cations in a solution of pH 7.7 whereas it becomes primarily permeable to anions if the pH is below 4.0. Mechanisms of ion permeation for various monovalent cations and anions were investigated at pH 7.7 and 3.9, respectively. Permeability ratios were obtained from the relationship between the membrane potential and the concentration of the test ions, and ionic conductances from current-voltage relations of the membrane. The permeability sequence for anions (SCN > I > NO3 > Br > ClO3 > Cl > BrO3 > IO3) was different from the conductance sequence for anions (Br, Cl > ClO3, NO3 > SCN). In contrast, the permeability and conductance sequences were identical for cations (K > Rb > Cs > Na > Li). The results suggest that anion permeation is governed by membrane charges while cation permeation is via some electrically neutral mechanism. |
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