Changes in intracellular K+ and Na+ ion concentrations during cell growth and differentiation

We compared intracellular K+ and Na+ ion concentrations during cell growth and differentiation of a mouse myeloid leukemia M1 cell line. Cells undergoing mitosis had higher K+ concentrations than quiescent cells. Treatment with a K+ channel blocker and furosemide enhanced cell growth and produced a slight increase in the intracellular K+ concentration. Treatment with reagents that reduced the intracellular K+ concentration stopped cell growth. Induction of differentiation in this cell line produced a decrease in the K+ concentration, which always was accompanied by an increase in the Na+ concentration. Treatment with ouabain, which decreased the intracellular K+ concentration, did not, however, induce differentiation in the M1 cell line. The data suggest that cell growth and differentiation in the M1 cells are accompanied by changes in the intracellular K+ and Na+ concentrations but that the changes in the contents of these monovalent cations do not necessarily induce differentiation in this cell line.