SERUM-INDUCED CELL-DEATH

In the culture system of human fetal lung fibroblasts (TIG-1) using Eagle's MEM containing various proportion of fetal bovine serum (FBS), FBS stimulated cell growth within the range below 40%. FBS at 60% and above inhibited cell growth in a dose-dependent manner and also induced cell death. As well as TIG-1, several types of cells presently tested also exhibited cell death in high concentration FBS. Bovine plasma also showed the same type of cytotoxicity as FBS. As a first step toward identifying the molecular basis of serum toxicity, FBS was divided into high and low molecular weight fractions by ultrafiltration and these were tested at various concentrations on variety of cell lines including TIG-1 human-fetal lung fibroblast, HeLa human epithelioid carcinoma cells, CPAE bovine aorta endothelial cell, FR Rat skin fibroblast, B16 mouse melanoma, and rat embryo primary cultures. When the macromolecular fraction was supplemented with inorganic salts and nutrients and its osmolarity was adjusted with Eagle's MEM, it showed no toxic effects over a blood range of concentrations. By contrast, a high concentration of low molecular- weight fraction induced cell death. These data suggest FBS contains low molecular-weight (< 1,000) factor(s) which cause cell growth inhibition and cell death.