Rates of Synthesis of Basement Membrane Proteins by Differentiating Teratocarcinoma Stem Cells and Their Modulation by Hormones

Abstract

The embryonal carcinoma mouse cell line F-9 was used as a convenient model for a quantitative study of the production of the basement membrane proteins laminin and type IV collagen. Both proteins could be identified in the culture medium and cell layer by radioimmuno assays, metabolic labeling and immunofluorescence. More than 95% of the material is secreted into the medium. Lack of ascorbic acid inhibits secretion of type IV collagen but not of laminin. Induction of differentiation into endoderm-like cells by retinoic acid consistently caused after a lag period of 2–3 days a 5–10 fold increase in the production of basement membrane proteins but not of total protein. Dibutyryl cyclic AMP further potentiated this specific effect particularly with respect to type IV collagen synthesis. Insulin, epidermal growth factor and nerve growth factor produced only moderate increases (10–60%) in the amount of laminin and type IV collagen. Effects of these hormones were only observed with certain doses and were quite variable between different experiments.