Cell cycle compartment analysis of Chinese hamster cells in stationary phase cultures.

Abstract

The distribution of Chinese hamster cells with respect to the compartments of the cell generation cycle was studied in cultures in the stationary phase of growth in two different media. A measure of the state of depletion of the nutrient medium was formulated by defining a quantity termed the nutritive capacity of the medium. This quantity was used to verify that the cessation of cell proliferation is due to nutrient deficiencies and not to density dependent growth inhibition. Cell cultures in stationary phase were diluted into fresh medium and as growth resumed, mitotic index, cumulative mitotic index, label index and viability were measured as a function of time. The distribution of cells with respect to compartments of the cell generation cycle in stationary phase populations was reconstructed from these data. Stationary phase populations of Chinese hamster cells that retained the capacity for renewed growth when diluted into fresh medium were found to be arrested in the G1 and G2 portions of the cycle; the relative proportion of these cells in G1 increased with time in the stationary phase, but the sequence differs in the two media. In early stationary phase, in the less rich medium, more cells are in G2 than in G1. Also in this medium a fraction of the population was observed to be synthesizing DNA during stationary phase, but this fraction was not stimulated to renewed growth by dilution into fresh medium.