Fibroblast growth factor release by bovine endothelial cells and human astrocytoma cells in culture is density dependent.
Basic fibroblast growth factor (bFGF) is a potent endothelial cell mitogen whose actions are mediated by binding to specific cell surface receptors on a variety of cell types. However, the amino acid sequence of bFGF does not contain a classical signal peptide sequence and the extent to which cellular stores of this mitogen are released is still a matter of some controversy. In the present study we examined the release of immunoreactive bFGF into serum-free conditioned medium of bovine corneal endothelial cells (BCE) and a human astrocytoma cell line, U87-MG. Western blotting analysis of BCE conditioned medium using N-terminal specific anti-bFGF serum revealed a single immunoreactive band of 32 kilodaltons, which was reduced to 18 kilodaltons in the presence of 8 M urea. Using a sensitive two-site immunoradiometric assay we were able to quantify the release of immunoreactive bFGF into the culture medium by BCE cells and by the human astrocytoma cell line U87-MG. In each case the release of bFGF was cell density dependent, but under all conditions the level of bFGF released was significantly greater in the transformed astrocytoma line, ranging from 15- to 50-fold higher than in the BCE cultures under various conditions. At 30% confluence the concentration of immunoreactive bFGF in the medium was maintained at a constant level for up to 24 h. However, the level of immunoreactive bFGF declined rapidly in confluent cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Sato
Y
Y
Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
Murphy
P R
PR
Sato
R
R
Friesen
H G
HG
D000818:Animals; D001254:Astrocytoma / Q000378:metabolism*; D015152:Blotting, Northern; D015153:Blotting, Western; D002417:Cattle; D002452:Cell Count; D002478:Cells, Cultured; D003470:Culture Media; D004728:Endothelium, Corneal / Q000378:metabolism*; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D006801:Humans; D007118:Immunoassay; D014407:Tumor Cells, Cultured / Q000378:metabolism
D003470:Culture Media; D005346:Fibroblast Growth Factors