The effect of serum starvation on DNA, RNA and protein synthesis during interphase in L-cells

Abstract

The effect of withdrawal of the serum complement from tissue culture growth medium (serum starvation) on synthesis of DNA, RNA and protein and on cell multiplication was studied in mouse fibroblasts in vitro (cell line L-929) by a combination of chemical and quantitative cytochemical methods. The first effect of serum starvation was seen on the synthesis of RNA, which was moderately depressed as early as 4–6 h after serum removal. Protein synthesis was relatively unaffected by serum starvation. The rate of DNA synthesis was unaffected for the first 10 h of serum starvation, but was depressed to about 1 3 of the normal value after 20 h of starvation. This effect on DNA synthesis was shown to be a combined effect on the initiation and rate of DNA synthesis. Cytophotometric DNA measurements on individual cells revealed that the observed inhibition of mitotic activity during serum starvation was not secondary to the inhibited DNA synthesis. Instead a direct effect on the conversion of G2-phase cells into the mitotic stage was observed to be at work, i.e. the serum complement in the growth medium seemed to be a factor of importance for the initiation of mitosis.