STRUCTURAL AND FUNCTIONAL-CHARACTERIZATION OF OSTEOGENIC GROWTH PEPTIDE FROM HUMAN SERUM - IDENTITY WITH RAT AND MOUSE HOMOLOGS

The osteogenic growth peptide (OGP) was recently characterized in rege nerating bone marrow. In experimental animals, OGP increases osteogene sis. Immunoreactive OGP (irOGP) in high abundance was demonstrated in normal animal serum mainly as an OGP-OGP-binding protein (OGPBP) compl ex. Here we show the presence of an OGP-OGPBP system in normal human s erum. The total irOGP content, of which the bound peptide comprises at least 80-90%, ranged from 480-4460 mu mol/L, several orders of magnit ude higher than that of other regulatory polypeptides. The steady stat e/total irOGP ratio declined between 23 and 49 yr of age. The bound ir OGP, purified by boiling, ultrafiltration, and hydrophobic high pressu re liquid chromatography, was identical to OGP obtained previously fro m rat regenerating marrow and mouse stromal cell cultures in terms of its amino acid sequence, immunoreactivity, and mitogenicity. These dat a demonstrate the usefulness of our immunoassay to measure circulating OGP. More importantly, the identity of the human OGP with that of oth er species indicates the peptide's evolutionary conservation and, thus , its biological importance. The natural occurrence of OGP In man sign ifies its potential role in the prevention of bone loss and rescue of bone mass, especially in osteoporosis.