A partially purified polypeptide fraction from rat liver cell conditioned medium with multiplication‐stimulating activity for embryo fibroblasts

Abstract

Abstract A polypeptide fraction with multiplication‐stimulating activity for chicken and rat embryo fibroblasts was partially purified from serum‐free medium conditioned by the growth of a line of rat liver cells. The specific multiplication‐stimulating activity of this fraction was 27,000 times that of serum. The rat liver cell multiplication‐stimulating activity had a molecular weight of approximately 10,000 daltons and was inactivated by mercaptoethanol and dithiothreitol. It had sulfation factor and non‐suppressible insulin‐like activities, but did not have anti‐trypsin activity. The rat liver cell multiplication‐stimulating activity resembled both multiplication‐stimulating activity from calf serum and somatomedin.