Activities of a cancellous bone-cell-stimulating substance.

A bone-cell-stimulating substance (BCSS) that initiates appositional bone formation in intact rats was examined for its effects on DNA and collagen synthesis in tibial and calvarial organ cultures of 17-day-old embryonic chicks. BCSS stimulated collagen synthesis in both types of bone. BCSS stimulated DNA synthesis in tibiae but inhibited synthesis in calvaria from the same chicks. Insulinlike growth factor, transforming growth factor-beta, platelet-derived growth factor, and fetal bovine serum also affected DNA synthesis differently in calvaria and tibiae. BCSS was able to modify some of the effects of these growth factors on DNA.