The partition of monovalent ions across the cell membrane

Shirley E. Simon ¹, B. M. Johnstone ², K. H. Shankly ³, and F. H. Shaw ³

¹ From the Department of Pharmacology, University of Melbourne, Australia. Mrs. S. E. Simon was the recipient of a Burroughs-Wellcome (Australia) Fellowship
² From the Department of Pharmacology, University of Melbourne, Australia. Mr. B. M. Johnstone was a General Motors-Holdens Fellow.
³ From the Department of Pharmacology, University of Melbourne, Australia.

The partition of Li⁺, Br^-, and I^- across the membrane of the sartorius muscle of the toad Bufo marinus has been investigated both at the steady state and with kinetic methods. Li⁺ was found to have access to an amount of muscle water similar to that of Na⁺. Br^- and I^- could be regarded as being interchangeable with cellular Cl^-. None of the foreign ions caused significant losses of cellular K⁺.

Li⁺ efflux from the cell was slower in muscles which were equilibrated for long periods in Li⁺ than in short equilibrated muscles. Na⁺ efflux from Li⁺-treated muscles was similar in rate to normal controls, but the amount of Na⁺ in the slow fraction was increased by Li⁺.

I^- efflux was extremely rapid, and it was not possible to differentiate kinetically between intra- and extracellular material.

These results have been found to be consistent with the hypothesis of a three phase system for muscle.

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