Isolation of the homogeneous constituents from non-diffusible sugar-peptide (NSP) fraction originating from bovine plasma--II. The influence on cell growth of BHK-21, BHK/RSV and PR-RSH cells in vitro.

1. The sugar-peptide aggregate isolated from the NSP fraction of bovine blood, added in concentration 20 microgram/ml, decrease of [3H]thymidine incorporation and cell proliferation of BHK-21 and BHK/RSV cells in vitro to approx. 25% of untreated control. 2. Two of four peptide constituents of the aggregate show distinct and extremely different effects on cell growth in vitro. The effects of peptide D mol. wt 5000-6000 is characteristic for peptide growth factors, while the peptide G mol. wt 1200-1800 decreases rapidly the growth of all investigated kinds of cells to 8-16% relative to untreated control. 3. The NSP fraction contains also two non-peptide constituents, which inhibit the growth of Rous sarcoma virus transformed cells to a statistically significant degree and have no effect on the growth of BHK-21 cells.