Biopotency of fetal bovine serum, and insulin and insulin-like growth factors I and II in enhancing whole-body protein synthesis of chicken embryos cultured in vitro.

Whole-body protein synthesis in chicken embryos was measured to examine the biopotency of fetal bovine serum, bovine insulin, recombinant human insulin, and recombinant human insulin-like growth factors (IGF) I and II. In all experiments chicken embryos at 7 days of incubation age were used and cultured in a synthetic serum-free medium in the presence or absence of the testing substances with a rotatory whole-embryo culture apparatus for up to 30 min. Whole-body protein synthesis was measured from the time course of specific radioactivities of free and protein-bound L-[4-3H]phenylalanine. In addition, the effect of bovine insulin on phenylalanine extraction rate from the culture medium was investigated. Supplementing the medium with fetal bovine serum and human IGF-I significantly enhanced whole-body protein synthesis. In contrast, human IGF-II, bovine insulin, or human insulin did not affect whole-body protein synthesis, although bovine insulin increased phenylalanine extraction rate from the culture medium in a proportional fashion as the dose increased. Therefore, from these results it was concluded that IGF-I, but not IGF-II, might be one of the anabolic factors in fetal bovine serum for stimulating whole-body protein synthesis, and that insulin may play a role in stimulating amino acid transport, but it may not be directly involved in protein synthesis of chicken embryos.