Effect of Physiologic Acids on Electrolytes in Rat Diaphragm

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Abstract
The effects of physiologic acids on muscle electrolytes were studied by incubating rat hemidiaphragms in Krebs-Ringer solution or blood at pH 7.4 and 6.8. With the addition of acetic, lactic or beta-hydroxybutyric acid to depress the pH, the sodium and potassium contents of muscles incubated in Krebs-Ringer solution were the same at each pH. This is in contrast to the efflux of these cations previously observed on adding hydrochloric acid to this medium. Using heparinized rat blood as the medium, the effect of hydrochloric acid was the same as in Krebs-Ringer solution. With acetic acid however, the pattern was reversed. Muscles in blood acidified with acetic acid actually retained more potassium than the controls at pH 7.4. An increased Pco2 to depress the pH in blood did not affect the potassium content, but there was a gain of sodium in the muscles in the more acid blood so that the net cation content increased. In contrast to the physiologic acids which can penetrate the cells as intact molecules, hydrochloric acid produces an essentially extracellular acidosis. Hydrochloric acid therefore causes a displacement of intracellular cation as hydrogen ions penetrate the cell. With blood, which is better buffered than the intracellular fluid, acetic acid and carbon dioxide depress the intracellular pH more than the extracellular pH. The pH gradient across the membrane is then analogous to that with hydrochloric acid but in the opposite direction resulting in a movement of cations into the cells.

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