A BONE-DERIVED GROWTH FACTOR ISOLATED FROM RAT CALVARIAE IS BETA2 MICROGLOBULIN

Abstract
Rat calvariae are known to secrete a bone-derived growth factor (BDGF) that stimulates bone DNA and collagen synthesis. BDGF was purified from calvarial culture medium with dialysis, gel filtration and HPLC. Amino acid composition of BDGF was compatible with murine B2 microglobulin (B2 m). and amino terminal sequence analysis revealed identity with mature murine B2 m. This was confirmed by Western blot analysis using a polyclonal antibody to B2 m. Like BDGF, human B2 m. stimulated bone DNA, collagen and noncollagen protein synthesis. Thus, BDGF, an autologous regulator of bone formation, is homologous to B2 m.