Changes in the concentration of insulin-like growth factor I and transforming growth factor beta1 in rat femoral bone...

Our knowledge of the concentration of growth factors in growing bone is limited. In the present study, we examined the developmental changes in the concentrations of insulin-like growth factor I (IGF-I) and transforming growth factor beta (TGF-beta) in the rat femur between weanling and maturity. We show that during the rapid growth phase there is a continuous rise in bone matrix IGF-I and TGF-beta in all compartments of the femoral bone. The association between IGF-I and TGF-beta is not only temporal, but with few exceptions is also observed within the animals of each age class. These data support the hypothesis that IGF-I and TGF-beta play an important role in the growth-associated accumulation of bone mass.