Biological properties and partial purification of a growth factor from porcine spleen.

3T3-Fibroblast growth is enhanced in a dose-dependent way by a factor isolated from porcine spleen after limited proteolysis. The factor is not dialyzable and is stable for 5 min at 100 degrees C and at pH 2 at room temperature. Trypsin or collagenase treatment does not affect its biological activity. The stimulation of cell growth is independent of serum concentration in the culture medium but is accelerated by insulin supplement. The biochemical properties of this factor indicate a novel growth promotor different from other growth factors.