Comparison of somatomedin activity in rat serum and lymph

A chick embryo fibroblast (CEF) assay has been used to measure the somatomedin activity in serum and lymph from normal rats. Lymph contains about one-half the SM activity found in serum. The somatomedin activites in serum and lymph have identical elution volumes on Sephadex G-50 in 1N acetic acid. Chromatography at neutral pH demonstrates that somatomedin peptides are bound to large proteins in both normal rat serum and lymph. The relative restriction of somatomedin to the intravascular space may be due to this protein binding.