| Abstract: | Using acid-ethanol extraction, two proteins with Mr=8 and 12 kD were extracted from rat glioma tissue induced with ethylnitrosourea. These proteins were shown to complete for the receptor with [125I]EGF (epidermal growth factor) on A431 cells. The 8 kD protein exhibited a marked mitogenic effect by stimulating DNA synthesis in resting NIH 3T3 cells. Stepwise chromatography of the acid-ethanol extract on Biogels P-60 and P-10 resulted in preparative amounts of the protein and allowed for its partial characterization. It was found that the half-maximum stimulation of DNA synthesis in NIH 3T3 cells was achieved at growth factor protein concentration of 5 micrograms/ml. The preparation obtained possessed the EGF-competing activity of 10 ng-equiv. EGF per 1 microgram of protein and stimulated protein phosphorylation of the 170 kD protein in NRK cell membranes. The data obtained suggest that this factor may be related to the family of the so-called EGF-like growth factors. |
