Inability of Serum to Completely Reverse Density-Dependent Inhibition of Cell Growth in Culture

Summary

Secondary cultures of mouse embryo cells showed density-dependent inhibition of growth when the medium contained 10% serum. After change of medium or addition of fresh serum, denslty-lnhlblted cells started synthesizing DNA and dividing. Synthesis of DNA began after a lag of about 12 hours, reached a maximum between 18 and 24 hours, and then declined gradually. The capacity of fresh serum to stimulate growth depended on the nutritional status of the medium to which it was added. Increase in the amount of serum in the culture medium increased the rate of DNA synthesis. However, DNA synth esis declined drastically as the medium became depleted, though it contained higher concentrations of serum. This indicated that nutrients and regulating micromolecules in the chemically defined medium are important in controlling the growth stimulated by serum and that serum does not have a nutritional function in monolayer cell culture.