Synthetic somatomedin C: comparison with natural hormone isolated from human plasma.

The biological and immunological properties of a chemically synthesized preparation of somatomedin C (Sm-C) were compared with those of the natural product isolated from human plasma. The two preparations produced identical curves in the radioimmunoassay and radioreceptor assay for Sm-C and in the radioreceptor assay for insulin. They were identical in their ability to stimulate DNA synthesis in confluent BALB/c 3T3 cells previously exposed to platelet-derived growth factor, and the biological activities of both preparations were completely neutralized by a monoclonal antibody raised against native Sm-C. These studies demonstrate that the chemically synthesized product is equivalent to the native molecule in all important respects and that it can be used interchangeably with the natural product for any studies that are contemplated.