Effects of temperature on growth rate of cultured mammalian cells (L5178Y).

L5178Y cells were cultured in vitro at various temperatures. When the cells were in the exponential growth phase, the cells were in the "steady state of growth," i.e., the fraction of cells in the G(1), S, G(2), and M stages and the durations of each stage were constant. The life cycle analysis of the cells in the steady state of growth demonstrated that the G(1) stage and the S stage were affected the most by variation of temperature, and suggested that these two stages have considerable influence on the growth rate of the L5178Y cells. The calculated activation energies were positive in each stage of the life cycle, whereas the entropies of activation were negative throughout. The possible significance of these findings in our search for the regulatory mechanisms of cell growth is discussed.