Detection of collagen degradation products from subcutaneously implanted organic bone matrix

Demineralized bovine bone powder was reduced with NaB3H4 to label the collagen crosslinks with tritium. The powder was enclosed in small nylon mesh pouches and implanted subcutaneously into rats for 3 weeks. Histological examinations revealed that multinuclear giant cells accumulated around the bone matrix, some in Howship's lacunae. Collagenous peptides containing intermolecular crosslinks were detected in the urea-soluble fraction extracted from the implant. Two crosslink-containing peptides were isolated from a dialyzable fraction: one contained dihydroxylysinonorleucine and the other hydroxylysinonorleucine. Both peptides had molecular weights of approximately 1000 estimated from the elution positions of gel filtration chromatography; and both had similar quantitative compositions of amino acids. There were no homologous peptides detected in a control experiment of the reduced bone matrix which was incubated in vitro with buffered saline for 1 week at 37 degrees C.