title: Enhancement of plasminogen activator activity by the culture medium of Rous sarcoma virus-transformed cells.
abstract: We have tested the effect of the culture medium of chicken embryo fibroblasts (CEF) transformed by Rous sarcoma virus (RSV) on plasminogen activator (PA) activity of normal and RSV-infected cells. The results obtained showed that fibrin digestion by cultures of normal uninfected and RSV-infected cells directly attached to a fibrin substrate was increased when the cells were exposed to the supernatant of an 18 h-culture of CEF transformed by RSV. Addition of cycloheximide to the supernatant completely abolished this effect. Similarly, exposure of both normal and RSV-infected cells to the culture medium of RSV-transformed CEF resulted in a marked increase of the soluble PA activity present in the supernatant. This effect, however, was not abolished by inhibition of protein synthesis. For both the cell-bound and soluble PA activities of normal and RSV-infected cells the stimulatory effect was transient, being maximal between 8 and 12 h of exposure to the transformed cell-conditioned medium and disappearing after 24 h. A possible correlation with transformation-enhancing factor(s), previously reported to be present in the culture medium of transformed cells, is discussed.
mesh_terms: D000818:Animals; D001358:Avian Sarcoma Viruses / Q000502:physiology*; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D002642:Chick Embryo; D003470:Culture Media / Q000032:analysis; D003513:Cycloheximide / Q000494:pharmacology; D005347:Fibroblasts; D010960:Plasminogen Activators / Q000378:metabolism*; D013696:Temperature; D013997:Time Factors
chemical_list: D003470:Culture Media; D003513:Cycloheximide; D010960:Plasminogen Activators