Potassium fluxes and ouabain binding in growing, density-inhibited and rous sarcoma virus-transformed chicken embryo cells

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Abstract
Potassium fluxes, ouabain binding, and Na+ and K+ intracellular concentrations were determined for cultures of growing normal, density‐inhibited and Rous sarcoma virus‐transformed chicken embryo fibroblasts. No significant differences in K+ influx or ouabain binding were detected between growing normal cells and Rous sarcoma virus‐transformed cells; however, ouabain binding and ouabain‐sensitive K+ influx were 1.5‐ to 1.8‐fold lower in density‐inhibited cells. Thus, potassium influx in this system can be classified as a growth‐related, but not transformation‐specific change. As determined by both flame photometry and radioisotopic (42K) equilibration, growing normal and density‐inhibited cells had similar potassium contents, whereas transformed cells exhibited 1.4‐fold higher potassium levels. Sodium ion levels, as measured by flame photometry, were also 2‐ to 4.5‐fold higher in transformed than normal or density‐inhibited cells. Complementary studies of potassium efflux showed a 1.3‐ to 1.5‐fold higher rate (based on the percentage of pool exiting the cell) in growing normal versus density‐inhibited or transformed fibroblasts. Because of the larger potassium pool in transformed cells, efflux based on absolute number of potassium ions is similar in normal and transformed chicken embryo fibroblasts.