Radioactive isotope labeled diffusible components of a bone morphogenetic substratum.

Bone matrix gelatin labeled with radioactive glucose, cysteine, proline, tyrosine or tryptophan was enclosed in one chamber while an adjoined second chamber was left empty to become filled with interstitial fluid. The paired diffusion chambers were implanted into the anterior abdominal wall of allogeneic rats for 14 days. Release of the matrix gelatin (BMG) from the loaded chamber was followed by a bone formation on the outer membrane of the unloaded chamber. 3H-cysteine labeled components of BMG were disseminated into the interstitial fluids and throughout the host tissues 5 times more rapidly than 3H-proline labeled BMG. The relative rates of loss of radioactivity from the residue was cysteine greater than tryptophan greater than tyrosine greater than proline. Electron microscopic autoradiography revealed random dissemination of collagenous and non-collagenous derivatives of BMG. 3H-glucose distribution was coordinated with ruthenium red staining coarse granules and may have originated from BMG. A component of interstitial fluid staining positively with Coomassie brilliant blue and PAS methods was identified by SDS polyacrylamide gel electrophoresis of interstitial fluid aspirated from empty chambers attached to chambers loaded with bone matrix gelatin. The character of the bone morphogenetic property in bone gelatin has not yet been defined in physico-chemical terms but present evidence points to the view that it is associated with a protein molecule.