Studies on the factors affecting cellular spreading upon culture-substrate: 1. the effects of divalent cations and conditioned medium on cellular spreading

Abstract

ABSTRACT The effects of various divalent cations on cellular spreading of in vitro cultured fibroblasts of chick embryos upon substrates were investigated in serum-free Eagle’s MEM. Fibroblasts spread on the surfaces of culture dishes in the presence of Mn2+, Mg2+, Ca2+ or Co2+, but not in the presence of Zn2+, Cd2+, Sr2+ or Cu2+. The minimum cation concentration for permitting cellular spreading at 37 °C is different for each cation. The values are 10−6, 5 × 10−4, 10−3 and 10−2 M for Mn2+, Mg2+, Ca2+ and Co2+, respectively. Below these concentrations the cells remain round. Mn2+ is about 1000-fold more effective in causing spreading than Ca2+. The cells do not spread at low temperature, but they do at 22 °C in the presence of 10−4 M Mn2+. In a medium conditioned with a mass culture of fibroblasts, cell spreading occurs at one tenth of the cation concentrations given above. If conditioned medium is heated at 65 °C for 30 min or treated with trypsin, its effect is abolished; this suggests that the effective factor(s) in the conditioned medium is a protein.