The effect of insulin-like growth factor analogs on turkey satellite cell and embryonic myoblast proliferation

The effects of several human and chicken insulin-like growth factor (IGF) a nalogs on turkey satellite cell and embryonic myoblast proliferation were e xamined in serum-free medium. Similar rates of proliferation were observed when human or chicken IGF-I or IGF-II (13.1 nM) was administered to satelli te cells. The biopotency of two analogs, which were modified to prevent int eraction with IGF-binding proteins, was also examined. Human Des(1-6)LGF-II was equipotent to native human and chicken IGF-II. However, the chicken LR 3 IGF-I analog was significantly less active toward satellite cells and emb ryonic myoblasts compared with chicken IGF-I. Human [Leu(27)] ICF-II, an an alog designed to have reduced affinity to the ICF Type I receptor but unalt ered binding to ICF-binding proteins, had a diminished effect on cell proli feration. Examination of IGF receptor binding characteristics revealed that chicken LR3 IGF-I had reduced ability to compete with [I-125]hIGF-I for bi nding to satellite cells or embryonic myoblasts compared with chicken ICF-I . The observed biological responses to IGF suggest that IGF-binding protein s have little effect on Type I IGF receptor action in these cell types in s erum-free medium. The results also suggest that alterations of the ICE mole cule to prevent interaction with binding proteins may also alter receptor b inding affinity.