Density-dependent growth adaptation kinetics in 3T3 cell populations following sudden [Ca2+] and temperature changes. A comparison with SV40-3T3 cells.

Lowered extracellular [Ca2+] cause low growth rates and low stationary cell densities in 3T3 cell cultures as compared to physiological [Ca2%]. Under otherwise constant conditions the extracellular [Ca2+] determines a stable stationary cell density, which can be reached by increase of net cell number or decrease of net cell number, depending on cell density at the time of [Ca2+] adjustment. SV40-3T3 cells do not show this [Ca2+] dependency. At 39 degrees C 3T3 and SV40-3T3 cell populations show an increased growth rate at low cell densities as compared to cell populations at 35 degrees C. Approaching the stationary density the growth rate of both cell sorts is reduced faster at 39 degrees C than at 35 degrees C, leading to lower stationary cell densities at 39 degrees C than at 35 degrees C. A temperature change from 39 degrees C to 35 degrees C or in the opposite direction can affect the stationary cell density of 3T3 cell populations only if applied before reduction of growth rate by density-dependent growth-inhibiting principles has taken place.