Serum-induced net K+ influx performed by the diuretic-sensitive transport system in quiescent NIH 3T3 mouse fibroblasts.

In serum deprived NIH 3T3 mouse cells the diuretic-sensitive transport system performs K+ self-exchange. The addition of serum which stimulates cell proliferation induces a net influx of K+, carried out by the diuretic-sensitive transport system. Thus, serum growth factors appear to induce a change in the mechanism of action of the diuretic-sensitive transporter from K+ self-exchange to an uphill transport pumping K+ into the cell. I propose here that this uphill uptake of K+ contributes to the increase of intracellular K+ content, found in the early G1 phase of the cell cycle.