Pituitary fibroblast growth factors: partial purification and characterization.

1. Isoelectric focusing of fractions derived from pH 7.0 extracts of bovine pituitary glands has been used to separate acidic and basic fibroblast growth factor (FGD) activity. FGF activity was assayed by measuring the initiation of DNA synthesis in Swiss mouse 3T3 fibroblasts. 2. Acidic and basic FGF activity present in crude extracts were not separated by chromatography on CM-Sephadex presumably because of association between acidic FGF and basic proteins. 3. Isoelectric focusing was used to separate acidic (pl 4-5) and basic (pI 8-9)FGF. The activity of acidic FGF was stable in urea and beta-mercaptoethanol, whereas basic FGF was inactivated. The activity of acidic FGF precipitated at pH 4.5 and was recovered when the precipitate was solubilized at pH 8, whereas basic FGF was soluble and stable at pH 4.5. 4. Acidic FGF at 10 ng/ml was as active as 1% fetal calf serum for the initiation of DNA synthesis. This potency is comparable with homogeneous preparations of basic FGF described in the literature.