Studies on Ion Accumulation in Muscle Cells |
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| Authors: | Gilbert Ning Ling and Margaret Mary Ochsenfeld |
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| Affiliation: | From the Department of Molecular Biology in the Department of Neurology, Division of Medicine, Pennsylvania Hospital, Philadelphia |
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| Abstract: | A comparison is made between the quantitative predictions of equilibrium ionic distribution in living cells according to the membrane theory (Donnan equilibrium) and according to the association-induction hypothesis. This comparison shows that both theories predict competitive effects of one permeant ion on the equilibrium concentration of another permeant ion; but within the limit of experimental accuracy only the association-induction model predicts quantitatively significant specific competition of one specified ion with the accumulation of another specified ion. The equilibrium distributions of K+, Rb+, and Cs+ ions in frog sartorius muscle were studied and quantitatively significant specific competition was demonstrated; these results favor the association-induction hypothesis (adsorption on cell proteins and protein complexes and partial exclusion from cell water). Based on this model we estimated that at 257deg;C, the apparent association constants for K+, Rb+, and Cs+ ion are 665, 756, and 488 (mole/liter)-1. We found that the total concentration of adsorption sites (no less than 240 mmole/kg of fresh cells) agrees with the analytically determined concentrations of β- and γ-carboxyl groups of muscle cell proteins (260 to 288 mmole/kg). |
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