Insulin-like growth factor (IGF) and bone.

Bone is not only a rich source of a diverse group of growth factors, but is also a very responsive tissue to such growth promoting agents. IGF-I and IGF-II are reported to be synthesized and retained in bone. While both IGF-I and IGF-II stimulate DNA, collagen, and noncollagenous protein synthesis in cultured calvariae, these explant cultures have quantitative differential sensitivities to these IGF's. In addition to the observed increase in collagen synthesis, collagen degradation decreased in calvariae treated with IGF-I or IGF-II.