Biochemical properties of the endothelium‐derived growth factor: Comparision to other growth factors

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Abstract
Cultured bovine aortic endothelial cells (BAEC) can be maintained at saturation density for several weeks in the absence of serum. These cells retain viability and normal culture morphology, and continuously produce a growth factor for mesenchymally derived cells–the endothelium‐derived growth factor (EDGF). The amount and specific activity of EDGF that is produced by BAEC under serum‐free conditions remains constant for weeks. The levels of EDGF produced under these serum‐free conditions is equivalent to levels produced in medium containing 5% plasma‐derived serum. EDGF has been found to be trypsin sensitive, acetone and ammonium sulfate precipitable, and resistant to heat and sodium dodecyl sulfate treatment. Gel filtration on Sephacryl S‐200 in the presence of formic acid (1%) yields two major peaks of activity corresponding to proteins of apparent molecular weights of approximately 24,000 and 14,000 daltons. This chromatographic step affords a ten‐to 12‐fold purification with a combined recovery of greater than 85%. Unlike brain or pituitary fibroblast growth factor, EDGF activity is destroyed by dithiothreitol or periodic acid. EDGF is not a somatomedin since it exhibits no detectable sulfation activity in a porcine cartilage assay. EDGF is not inhibited by antiserum to epidermal growth factor and is capable of stimulating DNA synthesis in a 3T3 variant cell line that is nonresponsive to and lacks receptors for epidermal growth factor. The majority of EDGF activity does not behave like the platelet‐derived growth factor during ion exchange chromatography. Antisera prepared in rabbits and in mice to human platelet‐derived growth factor has little effect on bivine or human EDGF activity. These biochemical and immunological properties of EDGF indicate that it is distinct from several other well‐characterized polypeptide growth factors.