Somatomedin-like activity from cultured embryo-derived cells: partial characterization and stimulation of production by epidermal growth factor (urogastrone)

Abstract

We have measured the appearance in cell culture media of a somatomedin-like activity (SLA) that cross-reacts in a basic-somatomedin radioreceptor assay and radioimmunoassay and that is produced by cultures of normal fetal-derived human (WI-38 fibroblasts) and mouse (embryonic palate) tissues and by cultures of a Simian virus 40 transformed WI-38 fibroblast cell line (WI-38 VA13/2RA subline). In addition to human growth hormone (hGH), epidermal growth factor (urogastrone) (EGF-URO), human placental lactogen (hPL), and porcine insulin (INS) were able to stimulate the production of SLA in serum-free cultures of the normal WI-38 fibroblasts; human prolactin (hPRL) caused only a marginal stimulation of SLA production in these cultures. In order of the magnitude of the stimulation of SLA production, the effects of the several hormones tested were [Formula: see text]. The half-maximal stimulatory effect of EGF-URO in the WI-38 cultures was observed at a concentration of about 1 nM. In the mouse palate organ cultures, EGF-URO also stimulated SLA production; the effect of EGF-URO was more pronounced in palate organ cultures derived from day 13 embryos compared with tissue obtained from embryos at days 14 and 15. The SLA produced by the human VA13/2RA subline was characterized further by gel filtration under acid conditions, by Procion dye column chromatography, and by high pressure liquid chromatography (HPLC). In terms of their immunoreactivity, adsorption to the dye column, and their apparent molecular weights (about 45 000), the SLA's produced by the VA13/2RA cells and the WI-38 cell cultures did not appear to differ. However, in terms of molecular weight and HPLC behaviour, the VA13/2RA-derived SLA was distinct from human basic somatomedin. We conclude that fetal-derived cells are capable of producing SLA in a manner that can be regulated both by a variety of polypeptide hormones and by the stage of embryonic development. Further, we conclude that the SLA produced by the fetal-derived human VA13/2RA cell line is indistinguishable from the SLA produced by WI-38 cells and that this SLA differs from the immunologically cross-reacting somatomedin that has been previously isolated from human plasma Cohn fraction.