Abstract
This brief review explores the role of intracellular K(+) during the transition of cells from quiescence to proliferation and the induction of apoptosis. We focus on the relationship between intracellular K(+) and the growth and proliferation rates of different cells, including transformed cells in culture as well as human quiescent T cells and mesenchymal stem cells, and analyze the concomitant changes in K(+) and water content in both proliferating and apoptotic cells. Evidence is discussed indicating that during the initiation of cell proliferation and apoptosis changes in the K(+) content in cells occur in parallel with changes in water content and therefore do not lead to significant changes in the intracellular K(+) concentration. We conclude that K(+), as a dominant intracellular ion, is involved in the regulation of cell volume during the transit from quiescence, and the content of K(+) and water in dividing cells is higher than in quiescent or differentiated cells, which can be considered to be a hallmark of cell proliferation and transformation.