Retention of sodium and chloride by mitochondria.

Abstract

Retention of sodium and chloride by washed mitochondria is described. The observations supplement data reported previously with respect to retention of potassium 1. 1. Only small amounts of sodium were retained after treatment with electrolyte-free sucrose: 0.025–0.05 μmoles/mg nitrogen or 1.0–2.0 μmoles/ml centrifuged pellet. This sodium was not found to be completely exchangeable with free sodium of the surrounding fluids, and influx of sodium from the medium was not dramatically stimulated by low concentrations (10−5 M) of inorganic mercuric salts. These findings differ from those reported with potassium and suggest retention by a different mechanism. 2. 2. Rates of influx of radioactive sodium or potassium into mitochondrial substance were inhibited by high concentration (10−1 M) of other cations in the suspending fluids. 3. 3. Washed mitochondria retained small amounts, also, of chloride: 0.03–0.05 μmole/mg nitrogen. Retention was increased 3–4 fold after treatment with 2,4-dinitrophenol, and this increase was associated with release of equivalent amounts of inorganic phosphate.