Further Studies on the Developmental Change in Myotrophic Activity of Chicken Serum: Relation between Activity and...

As an extension of previous studies, we reexamined the developmental change in trophic activity of chicken serum on chicken myogenic cells in vitro and attempted to elucidate it on the basis of possible changes in serum transferrin (Tf), the myotrophic activity of which depends both on its concentration and on the level of its iron-saturation. The myotrophic activity was found to be low until the second week in ovo, then to increase rather abruptly to a plateau at about the time of hatching, and then to decrease to the adult level. Determination of the concentration and level of iron-saturation of serum Tf suggested that the change in myotrophic activity was mainly caused by these two parameters, though another factor(s) may also be involved.