Abstract
PTH (0.5 unit/ml) and CT (0.5 unit/ml) strongly stimulated the in vitro growth of the chick embryo femur in terms of elongation and dry weight increase as well as an increase in the protein, hexosamine, hydroxyproline, DNA and RNA content of the femur. A synergistic effect was observed when PTH and CT were simultaneously added to the medium, suggesting that the mechanism of the growth stimulating effect of one of these hormones might be different from that of the other. The exposure of PTH to the femur caused an increase in cyclic AMP content. The direct addition of dibutyryl cyclic AMP (1 mm) to the medium mimicked the effect of PTH on the cartilage. PTH, therefore, seems to stimulate the growth of cartilage via the increase in cyclic AMP content of the femur. CT had no effect on the cyclic AMP content of the femur.
