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The effects of external sodium substitution on cell sodium and potassium in vascular smooth muscle
Author(s) -
Friedman Sydney M.
Publication year - 1977
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.1977.sp011946
Subject(s) - sodium , potassium , vascular smooth muscle , substitution (logic) , chemistry , smooth muscle , medicine , biophysics , endocrinology , biology , organic chemistry , computer science , programming language
1. The entry of Li into the vascular smooth muscle cells of the rat tail artery follows first‐order kinetics with a rate constant of approximately 1·3 hr −1 at 10 m M ‐[Li] o . The rate constant decreases gradually to ca. 0·5 hr −1 when the [Li] o /[Na] o ratio is increased. 2. Replacement of Na with Li over the range of [Li] o from 1 to 115 m M , accomplished at constant ionic strength and osmolarity of the bathing solution, produces changes in cell Na and K without apparent change in cell water. At equilibrium, cell Li increases in linear proportion to [Li] o , at a ratio of 2:1 throughout the range. The increase in cell Li is associated with inverse falls in both cell K and Na such that the ratio of cell K to cell Na remains constant at ca. 10:1 throughout. 3. The changes in the ionic contents, induced by equilibration of the tissue with a Na‐free, Li‐substituted solution, are reversible. 4. Replacement of Na with sucrose over the range of 40‐115 m M results, at equilibrium, in a linear fall in cell Na without conspicuous change in cell K. A constant portion of the cell Na, ca. 10 m‐mole/kg dry wt., does not participate in this exchange. 5. At equilibrium, reductions in [Na] o are reflected in corresponding reductions in apparent [Na] i such that the [Na] o /[Na] i ratio remains constant.