Changes in the concentration of insulin-like growth factor I and transforming growth factor beta 1 in rat femoral bone during growth

Our knowledge of the concentration of growth factors in growing bone is lim ited. In the present study, we examined the developmental changes in the co ncentrations of insulin-like growth factor I (IGF-I) and transforming growt h 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 ass ociation between IGF-I and TGF-beta is not only temporal, but with few exce ptions is also observed within the animals of each age class. These data su pport the hypothesis that IGF-I and TGF-beta play an important role in the growth-associated accumulation of bone mass.