[Proliferation and DNA synthesis in a CHO-K1 cell culture with a varying serum concentration in the medium]

The possibility of using CHO-K1 cells for investigation of mechanisms involved in stimulation of cell proliferation by serum has been studied. The decrease of serum content in the cultural medium down to 0.5% causes the arrest of cell growth and the lowering of DNA synthesis. The addition of fresh 10% serum stimulates DNA synthesis 12 hours later with the following renewal of cell proliferation. G1-period in cells synchronized by vinblastine is 6 hours. Thus, the removal of some serum factors form cultural medium causes a reversible arresting of CHO-K1 cell proliferation.