PARTIALLY PURIFIED REINDEER (RANGIFER TARANDUS) BONE MORPHOGENETIC PROTEIN HAS A HIGH BONE-FORMING ACTIVITY COMPARED WITH SOME OTHER ARTIODACTYLS

Noncollagenous proteins, including bone morphogenetic. protein (BMP), were extracted in 4 mol/l guanidinium hydrochloride (GuHCl) from the p ulverized and HCl-demineralized matrix of reindeer, bovine, sheep and porcine bone. To remove water-soluble material, the GuHCl solution was dialyzed against water and water-insoluble material and re-dissolved in 4 mol/l GuHCl. Gelatin peptides were removed by extraction in 0.25 mol/l citrate buffer (pH 3.1). The yield consisted mostly of large com plexes and protein molecules of molecular weight less than 35,000 dalt ons. Isoelectric focusing of the material showed three to four differe nt protein molecules: three acidic and one neutral. Bone-forming activ ity was investigated by implanting 0.6-15.0 mg of partially purified p rotein preparation into the thigh muscles of BALB mice. Radiologically detectable formation of new bone required 0.6 mg of reindeer BMP, 2.5 mg of bovine BMP, 5.1 mg of sheep BMP, and 8.0 mg of porcine BMP. A r ough estimate of the area of the deposits showed that reindeer BMP had the highest bone formation activity, and porcine had the lowest. The formation of new bone was confirmed histologically. It is suggested th at the differences in osteogenic activity are due to quantitative diff erences in BMP constituents or in the degree of complex formation in t he protein preparations. Also immune and other defense mechanisms may generate differences in osteogenic response.