Characterization of the insulin-like growth factor (IGF) axis in the serum of maternal and fetal macaques (Macaca mulatta and Macaca fascicularis).

The insulin-like growth factors (IGFs) are key effectors of fetal growth and development which are modulated by serum carrier proteins (IGF binding proteins [IGFBPs]). Studies were performed to evaluate the developmental profile of IGFs and IGFBPs in the macaque, an important nonhuman primate model for human development and disease. IGF-I, IGF-II, and IGFBP-3 were studied in the rhesus (Macaca mulatta) and long-tailed (Macaca fascicularis) monkey fetus and dam during the second and third trimesters of pregnancy. Serial fetal blood samples were collected by cardiocentesis every 10 days from gestational day (GD) 90-160, and at 1 month postnatal age; maternal blood samples were collected at similar timepoints. Results indicated that maternal sera IGF-I and IGF-II did not change significantly whereas fetal concentrations of serum IGF-I and IGF-II increased approximately two-fold during the second to the third trimesters. No significant differences were detected between the two species. Western-ligand blot analysis revealed predominant IGFBPs of 45-40 (IGFBP-3) and 28 kDa (IGFBP-1) in both the maternal and fetal compartments, and Western-immunoblot analysis using a specific antisera against IGFBP-3 indicated 45-40 and 28 kDa immunoreactive forms. Thus, although IGF-I, IGF-II, and IGFBP-3 remained relatively unaffected in maternal sera during this period of gestation, fetal concentrations of IGF-I, IGF-II, and IGFBP-3 increased in a developmental profile similar to the human fetus.