Potassium Transport in Single Mammalian Skeletal Muscle Cells during in vitro Incubation

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Abstract
Single skeletal muscle cells were isolated after varying intervals of in vitro incubation at 20–22°C from a muscle biopsy of the adductor muscle of dogs. From each isolated fibre 3–4 pieces, 70–90 μ long, were cut out and analyzed separately. Dry mass was calculated from x‐ray absorption measurements. The potassium content was determined from x‐ray fluorescence microanalysis and from ultra‐micro flame photometric analysis.During the first 30–40 rnin of in vitro incubation profound changes in cellular potassium content took place. Cells isolated during the first few min of incubation usually had a lower potassium content than cells isolated after 5 to 10 min. In the period 10 to 25 rnin after the initiation of incubation the cells started to loose intracellular potassium. This cellular potas sium loss was followed by a period of reaccumulation, since cells isolated 30 to 45 rnin after initiating incubation usually had a potassium content as high as that of cells isolated after 5 to 10 rnin of incubation. When the sodium pump was inhibited by addition of 10‐3M ouabain to the incubation medium or if glycolysis was inhibited by 10‐3M monoiodoacetate, no reaccumulation of intracellular potassium was seen. 10‐3M 2.4‐clinitrophenol produced a pro found rapid loss of cellular potassium. It therefore appears that the reaccumulation of cellular potassium after the period of cellular potassium loss was dependent on the integrity of the sodium pump and a source of energy. The possible basis for the profund cellular electrolyte changes which occur during in vitro incubation are discussed.